Unit 1.2:Kinematics

Question 1

Define Displacement

Answer 1

The distance an object travels in any given direction (positive or negative)

Question 2

Define velocity

Answer 2

The rate of change of displacement

Question 3

Define speed

Answer 3

Distance traveled per unit time

Question 4

Define Acceleration

Answer 4

Rate of change of velocity

Question 5

What 2 words are applied to both speed and velocity?

Answer 5

Mean and instantaneous

Question 6

What is the ‘mean’ speed/velocity?

Answer 6

The average measured over a significant amount of time

Question 7

What is ‘instantaneous’ speed/velocity?

Answer 7

The speed or velocity at any given instant

Question 8

How is mean speed calculated?

Answer 8

v-u/t

Question 9

How is instantaneous speed calculated?

Answer 9

Taking a tangent to the curve on a displacement-time graph or by taking a very small time interval.

Question 10

On a displacement-time graph, what is the gradient equal to?

Answer 10

The gradient is equal to the velocity

Question 11

On a velocity-time graph, what does the gradient represent?

Answer 11

Acceleration

Question 12

On a velocity-time graph, what is the area under the graph equal to?

Answer 12

The distance travelled

Question 13

State the 4 kinematic equations

Question 14

Derive the 4 kinematic equations

Question 15

How is terminal velocity achieved?

Answer 15

When the air resistance becomes equal to the weight

Question 16

On a displacement-time graph, what is the gradient equal to?

Answer 16

The gradient of the graph at any point is equal to the instantaneous velocity at that point.

Question 17

On a displacement-time graph, how do you calculate the average velocity?

Answer 17

Δx/t

Question 18

On a velocity-time graph, what does the gradient represent?

Answer 18

Acceleration

Question 19

On a velocity-time graph, what is the area under the graph equal to?

Answer 19

The distance travelled

Question 20

Derive v=u+at

Answer 20

Use of a= Δv/t

Question 21

Derive x=(v+u/2)t

Answer 21

Use of Vav=Distance/time and re-arrange

Question 22

Derive x=ut+½at²

Answer 22

Substitute v=u+at for v in x=(v+u/2)t

Question 23

Derive v²=u²+2ax

Answer 23

Re-arrange x=(v+u/2)t for t, and substitute t in V=u+at

Question 24

When air resistance is taken into account, does acceleration remain a constant?

Answer 24

No. When acceleration is taken into account, acceleration becomes non-uniform, and reduces to zero as the object gains speed

Question 25

Describe how a skydiver reaches terminal velocity.

Answer 25

At the beginning, the sky diver’s vertical speed is zero (or very close to zero), and hence there’s no air resistance.
There’s therefore a downward resultant force created by the weight. This causes the skydiver to accelerate downwards. As the skydiver’s speed increases, he/she pushes downwards on the air molecules with an
increasing force, since the air’s momentum is changing at a greater rate. Hence the air molecules, by newton’s 3rd law, are creating an upward force on the skydiver
(air resistance) that increases with speed.
Eventually, the air resistance becomes equal to the weight, and terminal velocity is reached.