P4: Explaining Motion

Question 1

What is the formula for working out speed?

Answer 1

Speed = Distance / Time

Question 2

What does the gradient of a distance-time graphy tell you?

Answer 2

Speed

Question 3

Whats the difference between speed and velocity?

Answer 3

Velocity is a vector quantity it has direction

Question 4

Explain how to find acceleration from a velocity-time graph

Answer 4

Acceleration is the gradient of the line

Question 5

What is an interaction pair?

Answer 5

When an object exerts a force on another object it experiences a force in return. These are interaction forces, they are equal and opposite

Question 6

A man leans on a wall with a force of 50N. What can you say about the force exerted by the wall?

Answer 6

The wall will exert a eqaul force of 50N in the opposire direction. It is reaction force

Question 7

Explain what the reaction of a surface is

Answer 7

Reaction force is an objects response to a force being exerted on it.

Question 8

DEFINE: Friction

Answer 8

Friction is a reaction force, when a object is moving relative to another one, both objects experience a force in the direction which opposes direction - this is friction

Question 9

Give two scenarios where forces are balanced

Answer 9

A car moving at a steady speed. If an object is stationary.

Question 10

What is meant by resultant force?

Answer 10

The resultant force is the overall force acting on an object - the force you get when you take into account (add up) all the individual and their directions

Question 11

If an object has 0 resultant force can it be moving? Can it be accerlating?

Answer 11

It is either stationary ot traveling at the same speed in the same direction

Question 12

What is the formula for change in momentum?

Answer 12

Change in Momentum = Resultant Force X Time it acts

Question 13

Explain how air bags, seat belts and crumple zones reduce the risk of serious injury in a car crash

Answer 13

In a collision you cant really affect the change in momentum. However the average force can be lowered by increasing the collision time ( time which the force acts). This is what car safety features do. Crumple zones increase the time taken for the cra to stop, air bags slow you down more gradually and seat belts stretch slightly increasing the time taken to stop - reducing forces on the chest.

Question 14

What is the formula for kinetic energy?

Answer 14

KE = 1/2 X MASS X (VELOCITY)^2