P2a Topic 3 - Motion and Forces

Question 1

Velocity is

Answer 1

How fast you’re going but it also must have a direction specified. The distance in a particular direction is called displacement.

Question 2

Speed=

Answer 2

Distance DIVIDED BY time

Question 3

Acceleration=

Answer 3

Change in velocity DIVIDED BY time taken

Question 4

Important notes for DISTANCE-TIME graphs

Answer 4

1) Gradient = speed.
2) Flat sections are where it’s stopped.
3) The steeper the graph, the faster it’s going.
4) Downhill sections means it’s going back towards the starting point.
5) Curves represent acceleration or deceleration.
6) A steepening curve means it’s speeding up.
7) A levelling off curve means it’s slowing down.

Question 5

How to calculate speed from DISTANCE-TIME graphs

Answer 5

It’s just the gradient. Change in Y over change in X.

Question 6

Important notes for VELOCITY-TIME graphs

Answer 6

1) Gradient = acceleration.
2) Flat sections represent steady speed.
3) The steeper the graph, the greater the acceleration or deceleration.
4) Uphill sections are acceleration.
5) Downhill sections are deceleration.
6) The area under any section of the graph is equal to the distance travelled in that time interval.
7) A curve means changing acceleration.

Question 7

How to calculate Acceleration and Distance from a VELOCITY-TIME graph

Answer 7

1) Acceleration is the gradient.

2) The distance travelled is equal to the area under the graph.

Question 8

For stationary objects

Answer 8

1) All forces are in balance.
2) Gravity is acting downwards.
3) This causes a reaction force from the surface pushing the object back up.

Question 9

For a steady horizontal velocity

Answer 9

1) All forces are in balance.

2) The thrust, reaction force, weight and drag all balance out.

Question 10

For a steady vertical velocity

Answer 10

1) All forces are in balance.

2) The drag and weight are equal.

Question 11

For horizontal acceleration

Answer 11

The forces are unbalanced

Question 12

For vertical acceleration

Answer 12

The forces are unbalanced

Question 13

Weight is

Answer 13

A force measured in newtons (N). Weight is caused by the pull of gravity.

Question 14

Mass is

Answer 14

NOT a force. It is just the amount of ‘stuff’ in an object. For any given object this will have the same value everywhere in the universe. Mass is measured in kilograms.

Question 15

Weight=

Answer 15

Mass TIMES BY gravitational field strength

Question 16

Falling objects in a vacuum accelerate at

Answer 16

The same rate

Question 17

Objects falling through an atmosphere reach a

Answer 17

Terminal velocity

Question 18

If object A exerts a force on object B then object B will exert the

Answer 18

Exact opposite force on object A.

Question 19

Speed is

Answer 19

Just how fast you are going with no regard to the direction

Question 20

If there is a zero resultant force acting on a body (the forces are balanced) then

Answer 20

The body will remain at rest, or else if it’s already moving it’ll just carry on at the same velocity.

Question 21

If the resultant force acting on a body is not zero, it will

Answer 21

Accelerate in the direction of the resultant force

Question 22

Force=

Answer 22

Mass TIMES BY acceleration