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P2.1 Forces and their effect
2.1.1 Resultant forces
2.1.2 Forces and motion
Forces can cause changes to the shape or motion of an object. Objects can move in a straight line at a constant speed. They can also change their speed and / or direction (accelerate or decelerate). Graphs can help us to describe the movement of an object. These may be distance–time graphs or velocity–time graphs.
You should be able to:
■ interpret data from tables and graphs relating to speed, velocity and acceleration
■ evaluate the effects of alcohol and drugs on stopping distances
■ evaluate how the shape and power of a vehicle can be altered to increase the vehicle’s top speed
■ draw and interpret velocity–time graphs for objects that reach terminal velocity, including a consideration of the forces acting on the object
Key words ForceMotionResultantStationaryVelocityAccelerationMassGradientSpeedStopping distanceReaction time
FrictionKinetic energyTerminal velocityElasticPotential energyWorkPowerMomentumConservation of momentum
If something is moving there is a force acting on it
To move something we need a force
A force is needed to change the shape of something
A force is a type of energy
Weight is a force
Mass is a force
Stretching a spring needs a force
A frictionless car does not need a force to keep it moving
Gravity is a type of force
Friction is a type of force
Forces always occur in pairs
P2.1.1 Resultant forcesa) Whenever two objects interact, the forces they exert on each other are equal and opposite.
b) A number of forces acting at a point may be replaced by a single force that has the same effect on the motion as the original forces all acting together. This single force is called the resultant force.
c) A resultant force acting on an object may cause a change in its state of rest or motion.
d) If the resultant force acting on a stationary object is:
■ zero, the object will remain stationary
■ not zero, the object will accelerate in the direction of the resultant force.
𝑎=𝐹𝑚
P2.1.2 Forces and motiona) The acceleration of an object is determined by the resultant force acting on the object and the mass of the object.F = m × a
b) The gradient of a distance–time graph represents speed.
c) Calculation of the speed of an object from the gradient of a distance–time graph.
d) The velocity of an object is its speed in a given direction.
e) The acceleration of an object is given by the equation:
𝑎=𝑣−𝑢𝑡
f) The gradient of a velocity–time graph represents acceleration.
g) Calculation of the acceleration of an object from the gradient of a velocity–time graph.
h) Calculation of the distance travelled by an object from a velocity–time graph.
Travel graphs
Is Dolly a clone of sheep A or B?
Explain your answer.
Dolly is a clone of sheep ........................
reason why