Motion&

Movement

Learning Objectives• Can define what a force is• Can explain Newtons 3 laws of motion• Understand the 3 types of motion• Can place this information into a variety

of sporting examples

Success Criteria• Can define Force• Can recall Newtons 3 laws with

examples• Can place the types of motion into

examples

WHAT IS A FORCE?

• With a partner 30 seconds discuss

FORCE is........

• A push or pull that alters, or tends to alter, the state of motion of a body– The force applied to the trampoline to allow the

downward phase of a jump to change to the upward phase of the next jump

– On mini whiteboard give an example and show me

1995?This is a perfect example of when everything came together within a sporting context.

It shows ultimate knowledge, control and execution of internal and external forces to break the World Record.

A distance that still stands since 1995

Jonathan Edwardshttp://www.youtube.com/watch?v=dFt9Yzp484c

FORCE• FORCE is push or pull• the unit is the NEWTON

(10 N is approx the weight of 1 kg)• force changes the state of motion of an object• force causes acceleration or deceleration or

change of direction• the more force the bigger the acceleration• force changes the shape of an object• WEIGHT, FRICTION, REACTION FORCES, AIR RESISTANCE / FLUID

FRICTION– all these forces affect the sportsperson

The 3 Lawshttp://www.youtube.com/watch?v=iH48Lc7wq0U

Newton’s First Law - INERTIAAn object will continue in a state of rest or uniform motion unless acted upon by an external force.

• If an unbalanced force acts on an object, it will accelerate in the direction of the unbalanced force.

• If an object is given a certain initial velocity and there are no unbalanced forces acting on it, the object will continue along its original path in a straight line.

INERTIA

Give 3 examples from sport where you may see this law in practise:

1.2.3.

Where is the only location where inertia cannot be influenced?

Staying in the blocks in a 100m sprintA cricket ball will keep travelling after being hit for a 6The High Jumper will keep going up over the bar

In space inertia cannot be influenced by external factors therefore on Earth everything can be influenced. The sprinter will not stay in the blocks for ever and the ball will fall and the higher jumper won’t always clear a height...why?

Newton’s Second Law - Acceleration

When a force acts on an object, the object is accelerated by an amount directly proportional to the force applied and inversely proportional to the mass of the object (F = ma) force = mass x acceleration

• The greater the force being exerted on an object, the faster the object moves.

• The greater the mass of the object, the

slower the object will move in relation to a lighter object with the same force applied.

A big mass (tennis ball)

is harder to accelerate

than a smaller mass

(table tennis ball).

Simply: 10N force against a tennis ball or a shot putt which travels furthest

Newton’s Second Law - Hockey• If a player strikes the ball, its acceleration

is determined by the mass of the ball and how hard the player hits it (F = ma).

• If the ball were heavier (larger mass), it would accelerate less.

• If the player hits the ball harder (larger force), the ball accelerates more quickly.

F

M A

Newton’s Second Law - Baseball

• A baseball player on deck getting ready to bat adds weights to their bat to practice swinging, and to warm up their muscles.

• If the total mass of the weights added is equal to the initial mass of the bat, then the weight is doubled.

• If the batter swings at a constant speed (a), and applies a uniform force throughout (F), we can apply Newton’s Second Law.

• When he removes the weights, the mass is cut in half, and the acceleration will be twice as fast as before.

A batter gets an advantage if

he uses Newton’s Second Law

before stepping onto the plate.

Newton’s Second Law - BaseballQ1. A batter swings with 200N of force on

deck circle, with weights attached making the bat twice as heavy as usual. What is the bat’s acceleration:a) on the on deck circle?b) at the plate when the weights

have been removed?

Q2. A bat has an acceleration of 80m/s2.What force was applied to the bat?

Q3. A batter at the plate swings with a force of 100N. What is the bat’s acceleration? How does this compare to the answer to Q1.b? Note: A bat has a mass of 2 kg.

Newton’s Second Law - BaseballA1. a) F = ma b) F = ma

a = F/m a = F/m a = 200N/4kg a = 200N/2kg a = 50m/s2 a = 100m/s2

A2. F = ma F = 2kg x 80m/s2 F = 160N

A3. F = ma The force applied is a = F/m half that in Q1.b, a = 100N/2kg therefore, the a = 50m/s2 acceleration is halved.

Newton’s Third Law - Reaction“For every action there is an equal and opposite reaction”

• For every force between two objects there is always an equal but oppositely directed force.

• The normal reaction force isthe support force exerted uponan object which is in contactwith another stable object.

Question:

When hitting a baseball,

if we call the force on the

bat against the ball the

action force, what is the

reaction force?

Normal reaction

force

Weight

Newton’s Third Law• When a swimmer turns, the pool wall pushes

against the swimmer with the same force as the swimmer pushes against the pool wall.

• When a weightlifter pushes against the ground, the ground pushes against the weightlifter with the same force.

• When a tennis player hits a ball with their racquet, the tennis ball exerts an equal but opposite force on the player’s racquet.

Can you think of any more examples?

Answer:The reaction force is the force exerted by the ball on the bat.

Newton’s Third Law - Hockey

• For every force exerted by an object, an equal and opposite force is exerted on the object.

HomeworkSentence Summary:

• Write a series of sentences to summarise Newton’s Laws.

• Give examples of two Olympic sports you can show Newton’s Laws working.

• Write an equation for the 2nd law

Success Criteria• Can define Force• Can recall Newtons 3 laws with

examples• Can place the types of motion into

examples

MOTION

MOTIONMotion is movement and is divided into 3 main categories:

• LINEAR MOTION GENERAL MOTION

• ANGULAR MOTION

LINEAR MOTION

• When a body moves in a straight or curved line with its parts moving the same distance in the same direction at the same speedE.g.. A tobogganistShot put ( curved line with no spin imparted at release)What else?......Show me......Linear motion occurs when a force is applied through the centre of mass of the body/object

ANGULAR MOTION

• When a body or part of a body moves in a circle or part of a circle about a particular point called the axis of rotation.

-Bicycle wheel-Movement around our joints (fixed points)-Front crawl in swimming (ARMS)-The high bar in men’s Olympic gymnastics

GENERAL MOTION

A combination of linear and angular motion

• Javelin thrower• Wheel chair athlete• Sprinter • Swimmer

This is by far the most common motion type in Sport

Examples of motion in sportLinear:http://www.youtube.com/watch?v=GSrpo_XDMR4&feature=relatedhttp://www.youtube.com/watch?v=nJ5gL8avcOo

Angular:http://www.youtube.com/watch?v=AQLtcEAG9v0http://www.youtube.com/watch?v=S6lzwT6nSdc

General:http://www.youtube.com/watch?v=Zkt-4MZxtjQ

TASK

• IN GROUPS USING AS MANY DIFFERENT SPORTS AS YOU CAN THINK OF, LIST:– Three examples of pure linear motion– Three examples of pure angular motion– Three examples of general motion

CENTRE OF MASS

• The ‘Centre of Mass’ is where the weight of a body tends to be concentrated.

• This is the point at which the body is ‘balanced in all directions’

Therefore in objects such a tennis balls and shot putts the c.o.m. Would be at the very core.

• However c.o.m. can be outside the body. In humans this is not in the same position but moves constantly as we do.

• A coit used in primary schools for play the c.o.m. Is in the centre, but there is nothing there

A prime example in sport is the high jump

At this moment the c.o.m. is outside the body underneath the back

It is only really feasible in moving objects especially people and animals that the c.o.m. Is identified if the body is STABLE.

Stability is important for balance, gymnastics is a good example such as the beam

Stability is dependent upon these factors:

• Position of the centre of mass• Base of support• Performers line of gravity• Mass of the performer

Stability

Centre of Mass

Line of Gravity

1. This is a stable position because….

2. It would become less stable by……

Base of Support

Centre of Mass and Application of Force

• The direction of the force being applied, in relation to the centre of mass, will dictate if the motion is linear or angular.

• If the line of the force is through the centre of mass the resulting motion will be linear. This is called a direct force.

• If the line of force passes outside the centre of mass the motion will be angular.This is called an eccentric force.

Centre of Mass and Application of Force

Force applied through centre of mass – direct force.

Ball goes up but with no spin – linear motion.

Force applied to side of ball – eccentric force.

Ball spins – angular motion.

Lin

er

Moti

on

An

gu

lar

Moti

on

The more spin needed the greater the force and the further away from the centre of mass it needs to be applied.