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Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter...

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Chapter Introduction Lesson 1 Work and Power Lesson 2 Using Simple Machines Chapter Wrap-Up
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Page 1: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

Chapter Introduction

Lesson 1 Work and Power

Lesson 2 Using Simple Machines

Chapter Wrap-Up

Page 2: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

How do machines make doing work easier?

Page 3: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

Essential Questions

• What is the relationship between work, power and efficiency?

Work and Power

Page 4: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

Work

Power

Efficiency

Work and Power

Page 5: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• In science, work is what is necessary for a force to move an object through a distance.

What is work?

• Work is calculated by multiplying the force applied to an object by the distance the object moves.

Page 6: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• In order for you to do work, two things must occur:

– You must apply a force to an object.

– The object must move in the same direction as your applied force.

What is work? (cont.)

Page 7: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Is work being done?

– Pushing a grocery cart in a store?

• Yes, because the cart is moving in the same direction as the force (push).

– Standing and holding a bag of groceries?

• No, Although you are applying a force to the grocery bag by holding it, the grocery bag is not moving so no work is done.

What is work? (cont.)

Page 8: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Work is important in science because it is related to energy.

• Work done when you lift an object which also increases the object’s energy.

– Moving objects have kinetic energy

– Gravitational Potential Energy (GPE) of an object increases as its height above the ground increases.

What is work? (cont.)

Page 9: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Doing work on a tray transfers energy to the tray. The added energy can be either kinetic energy or potential energy.

What is work? (cont.)

Page 10: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

How is work measured? (cont.)

• Work is equal to the force of a push or a pull multiplied by the distance the object is moved.

• The product of force and distance has the unit newton·meter. The newton·meter is also known as the joule (J).

Page 11: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

How is work measured? (cont.)

Page 12: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The work done on an object depends on the direction of the force applied and the direction of the motion.

How is work measured? (cont.)

Applied

Force

Motion of bed

Page 13: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Now think of a box being pulled by a rope.

– In this scenario, the applied force is at an angle (from your arm to the rope). The applied force has a horizontal part and a vertical part.

How is work measured? (cont.)

Applied force

Horizontal force

Vertical force

Motion of the box

Page 14: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• When the applied force and the motion of the object are NOT in the same direction, only the part of the force that is in the same direction as the motion of the object is used in the work equation.

• The vertical part of the applied force does no work on the box because it is not in the same direction as the motion of the box.

Motion of the box

Horizontal force

Vertical force

How is work measured? (cont.)

Page 15: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The work done to lift an object equals the weight of the object multiplied by the distance it is lifted.

– Work = weight x distance

How is work measured? (cont.)

Page 16: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Power is the amount of work done per unit of time.

• You can also think of power as how fast energy is transferred to an object.

What is power?

Page 17: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• You can calculate power by dividing the work done by the time needed to do the work.

• Power is expressed in joules per second(J/s). One Joule per second is also know as a watt (W).

What is power? (cont.)

Page 19: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• A machine is any device that makes doing something easier.

• Some machines are simple and other machines are more complex.

What is efficiency?

Page 20: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The force you apply to a machine is the input force.

• The machine changes the input force to an output force.

What is efficiency? (cont.)

Input force

Output force

Page 21: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The amount of input force multiplied by the distance over which the input force is applied is the input work.

• Winput = Finput x dinput

What is efficiency? (cont.)

Input force

Distance applied

Page 22: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Machines convert input work to output work by applying an output force on something and making it move.

– Woutput = Foutput x distanceoutput

What is efficiency? (cont.)

Output force

Output distance

Page 23: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The output work done by a machine never exceeds the input work because of friction.

– Friction converts some of the input work to thermal energy.

What is efficiency? (cont.)

Page 24: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Efficiency is the ratio between the work done by a machine and the work put into it.

• Because output work is always less than input work, a machine’s efficiency is always less than 100 percent.

– Ex. Elevators are 85% efficient, car motors are 17% efficient

What is efficiency? (cont.)

Page 25: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

What is efficiency? (cont.)

Page 26: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

When you lift an object, what else are you doing?

A. decreasing the object’s energy

B. increasing the object’s energy

C. making the object do work

D. receiving the object’s energy

Page 27: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. energy

B. force

C. power

D. work

Which is the rate at which work is done?

Page 28: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. distance the object is lifted

B. energy used to lift the object

C. force applied to the object

D. power needed to lift the object

To calculate the work done lifting an object, which is multiplied by the weight of the object?

Page 29: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

Essential Question

• What is the relationship between work input and work output in a simple machine?

Using Simple Machines

Page 30: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

Simple machine

Mechanical advantage

Lever

Fulcrum

Using Simple Machines

Wheel and axle

Pulley

Inclined plane

Screw

Wedge

Page 31: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Simple machine is a device with few, if any, moving parts that makes it easier to do work.

– Ex. screwdriver

• A machine makes work easier by changing the size of the force, the distance the force acts, or the direction of a force.

What is a simple machine?

Page 32: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The two main classes of simple machines are the lever and the inclined plane.

• Lever class includes:

– Wheel and axle and the pulley

What is a simple machine? (cont.)

Page 33: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Inclined plane includes:

– Wedge and screw

What is a simple machine? (cont.)

Page 34: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Mechanical advantage is the number of times a simple machine multiplies an effort force.

What is a simple machine? (cont.)

Page 35: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Mechanical advantage can be less than 1, equal to 1, or greater than 1.

• A mechanical advantage greater than 1 means the output force is greater than the input force.

What is a simple machine? (cont.)

Page 36: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

What is a simple machine? (cont.)

Page 37: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Lever is a simple machine consisting of a bar and a pivot point.

– Fulcrum is the pivot point in a lever.

• The part of the bar on which a person applies an effort force is called the effort arm.

What are the three kinds of levers?

Page 38: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The part of the bar on which the lever produces an output force is called the resistance arm.

• The position of the fulcrum, the effort arm and the resistance arm vary among levers.

What are the three kinds of levers? (cont.)

Page 39: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• In a first-class lever, the fulcrum is between the input force and the output force.

• The direction of the input force is opposite the direction of the output force.

• When the effort arm is longer than the resistance arm, the output force is greater than the effort force

What are the three kinds of levers? (cont.)

Page 40: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Your neck is an example of a first-class lever.

What are the three kinds of levers? (cont.)

Page 41: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• A second-class lever has the output force between the input force and the fulcrum.

• The output force and the input force act in the same direction.

• A second-class lever makes the output force greater than the input force.

What are the three kinds of levers? (cont.)

Page 42: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• A wheel barrow is an example of a second-class lever.

What are the three kinds of levers? (cont.)

Page 43: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• A third-class lever has the input between the output force and the fulcrum.

• The output force is less than the input force.

• Both the input force and the output force act in the same direction.

What are the three kinds of levers? (cont.)

Page 44: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A fishing rod is an example of a third-class lever.

What are the three kinds of levers? (cont.)

Page 45: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The ideal mechanical advantage of a lever equals the length of the input arm divided by the length of the output arm.

What are the three kinds of levers? (cont.)

Page 46: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

What are the three kinds of levers? (cont.)

Page 47: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Wheel and axle is a simple machine that consists of a wheel that applies an effort force and a smaller axle that produces an output force.

• Mechanical advantage of a wheel and axle is calculated by dividing the length of the effort arm by the length of the resistance arm.

What other machines are like levers?

Page 48: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• For a wheel and axle, the length of the input arm is the radius of the wheel and the length of the output arm is the radius of the axle.

• A screwdriver is a wheel and axle. The handle is the wheel and the shaft is the axle.

What other machines are like levers? (cont.)

Page 49: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• A wheel and axle can also make work easier in another way.

– If the radius of the wheel is smaller than the radius of the axle, the output distance is increased and the output force is decreased.

– Ex. Helicopters and ceiling fans.

What other machines are like levers? (cont.)

Page 50: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Pulley is a grooved wheel that turns by the action of a rope in the groove.

What other machines are like levers? (cont.)

• In a pulley, the rope forms the arms and the wheel serves as the fulcrum.

Page 51: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• A pulley can be fixed or movable.

What other machines are like levers? (cont.)

• A fixed pulley makes work easier by changing the direction of the effort force.

Page 52: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Movable pulleys are attached to the object being lifted and decrease the force needed to lift the object.

• A single movable pulley multiplies the effort force by 2, so it has a mechanical advantage of 2.

• A single movable pulley does not change the direction of the effort.

What other machines are like levers? (cont.)

Page 53: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The ideal mechanical advantage of a pulley or a pulley system is equal to the number of sections of rope supporting the object.

What other machines are like levers? (cont.)

Page 54: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Inclined plane is a straight, slanted surface that can multiply an effort force.

• It takes less force to move an object upward along an inclined plane than it does to lift the object straight up.

What are inclined planes?

Page 55: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The mechanical advantage of a ramp is equal to the output force divided by the effort force.

What are inclined planes? (cont.)

Page 56: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The ratio of output force to effort force is the same as that of effort distance to output distance.

• For this reason, a ramp’s mechanical advantage can also be found by dividing the length of the incline by its height.

What are inclined planes? (cont.)

Page 57: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Calculate the mechanical advantage of each inclined plane.

What are inclined planes? (cont.)

Length = 2.0m, height = 1.0m

IMA = 2 ÷ 1 = 2

Length = 5.0m, height = 3.0m

IMA = 5.0 ÷ 3.0 = 1.7

• The longer and shallower the ramp, the greater the mechanical advantage.

Page 58: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Screw is a simple machine made of an inclined plane wrapped around a central bar that can multiply an effort force.

What are inclined planes? (cont.)

• Spiral ridges called threads move into an object as the head of the screw turns.

• The space between the threads is called the pitch.

Page 59: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The mechanical advantage of a screw and ramp are calculated in a similar way.

What are inclined planes? (cont.)

• IMA = effort distance

output distance

• The effort distance is the distance around the head and the output distance is the pitch of the screw.

Page 60: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• Wedge is an inclined plane that changes the direction of an applied force.

• A wedge can be a single inclined plane or two inclined planes joined back to back.

• The thinner the wedge, the greater the mechanical advantage.

What are inclined planes? (cont.)

Page 61: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• When two or more simple machines are combined, they form a compound machine.

What are compound machines?

• Levers, screws, wheels and axles and gears combine to make a bicycle, a compound machine.

Page 62: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• The efficiency of a compound machine is calculated by multiplying the efficiencies of each simple machine together.

• Each simple machine decreases the overall efficiency of the compound machine.

• Lubricants, such as oil, reduce the amount of energy that is wasted as heat.

What are compound machines? (cont.)

Page 63: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

What are levers, wheels and axles, inclined planes, wedges, screws, and pulleys examples of?

A. complex machines

B. compound machines

C. idea machines

D. simple machines

Page 64: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. fulcrum

B. inclined plane

C. screw

D. wheel

Which uses less force to raise an object compared to lifting the object straight up?

Page 65: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. gear

B. pulley

C. screw

D. wedge

Which is a simple machine consisting of a grooved wheel with a rope or cable wrapped around it?

Page 66: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

Visual Summary

Chapter Review

Standardized Test Practice

Page 67: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A machine makes work easier by changing the force that is needed or the direction or the distance through which a force is applied.

Page 68: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

• For work to be done on an object, an applied force must move the object.

• When work is done on an object, the energy of the object increases.

• Power is the rate at which work is done.

• Because of friction, the output work done by a machine is always less than the input work to the machine.

• Friction between moving parts converts some of the input work into thermal energy and decreases the efficiency of the machine.

Lesson 1: Work and Power

Page 69: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

Lesson 2: Using Simple Machines

• Simple machines make it easier for people to do work. They have few, if any, moving parts.

• Machines make work easier by changing the size of the force required, the distance over which the object moves or the direction of the required force.

• The mechanical advantage of a machine is the ratio of the output force to the input force.

• A compound machine is made of two or more simple machines that operate together.

Page 70: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. distance and length

B. force and distance

C. force and power

D. height and weight

What two things must you know to calculate work?

Page 71: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. distance

B. force

C. time

D. weight

What do you divide work by to calculate power?

Page 72: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. energy

B. input force

C. output force

D. power

Which refers to the force you apply to a machine to make it work?

Page 73: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. output power

B. output force

C. mechanical advantage

D. input force

What does a machine apply to an object?

Page 74: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. axle

B. fulcrum

C. screw

D. wedge

What does a lever rotate around?

Page 75: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. distance

B. energy

C. force

D. power

What is transferred when work is done?

Page 76: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. power

B. force of the motion

C. distance of the motion

D. direction of the motion

The work done on an object depends on the direction of the force applied and which of these?

Page 77: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. efficiency

B. equal output

C. mechanical advantage

D. output work

What is the ratio of a machine’s output force to its input force?

Page 78: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. fulcrum

B. lever

C. wedge

D. wheel and axle

What is a simple machine made of a bar that rotates about a fixed point?

Page 79: Chapter Introduction Lesson 1Lesson 1Work and Power Lesson 2Lesson 2Using Simple Machines Chapter Wrap-Up.

A. wedge

B. screw

C. fulcrum

D. axle

What term describes an inclined plane wrapped around a cylinder?


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