Topic 2 - Motion And Forces

Question 1

What is a scalar quantity?

Answer 1

A quantity that only has magnitude but no direction.

Question 2

What is a vector quantity?

Answer 2

A quantity that has both a magnitude and an associated direction

Question 3

Three examples of vector quantities

Answer 3

Velocity
Displacement
Force

Question 4

Give examples of scalar quantities

Answer 4

Temperature 
Mass 
Time
Speed 
Distance 
Energy

Question 5

What is velocity

Answer 5

The speed of an object in a specific direction.

Question 6

Equation relating average speed, distance and time

Answer 6

Average speed = distance / time

Question 7

On distance/time graph, what value does the gradient of the line represent?

Answer 7

The speed

Question 8

On a displacement/time graph, what value does the gradient of the line represent?

Answer 8

The velocity

Question 9

What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?

Answer 9

Draw a tangent to the curve at the required time

Calculate the gradient of the tangent

Question 10

Equation for the average acceleration of an object

Answer 10

Acceleration = (change in velocity)/(Time taken)

A = (v-u)/t

Question 11

Equation final velocity with initial velocity, distance and acceleration

Answer 11

V^2 - U^2 = 2 x a x x

Question 12

How can the distance travelled by object be calculated from a velocity-time graph?

Answer 12

It is equal to the area under the graph

Question 13

On a velocity/time graph what does the gradient of the graph represent?

Answer 13

The acceleration

Question 14

Typical value of the speed of sound

Answer 14

330m/s

Question 15

Typical value for human walking speed

Answer 15

1.5m/s

Question 16

What is a typical value human running speed?

Answer 16

3m/s

Question 17

What is a typical value for human cycling?

Answer 17

6m/s

Question 18

What is weight?

Answer 18

The force that acts on an object due to gravity and the objects mass.

Question 19

Weight unit

Answer 19

N (newton)

Question 20

Gfs unit

Answer 20

N/kg

Question 21

When can an object travelling at a constant speed not have a constant velocity?

Answer 21

When the object is changing direction; for example, moving in a circle

Question 22

Why does an object travelling at a constant speed in a circle not have a constant velocity?

Answer 22

Speed is a scalar quantity
Velocity is a vector quantity which means it can only be constant if the direction is constant.
In circular motion, the direction is continuously changing
Velocity is constant changing

Question 23

What is the resultant force that acts on an object moving in a circle called, and in which direction does it act?

Answer 23

It is called the centripetal force and acts towards the center of the circle

Question 24

What is inertial mass?

Answer 24

A measure how difficult it is to change a given object’s velocity
The ratio of force over acceleration

Question 25

State Newton’s third law

Answer 25

Whenever two objects interact, the forces that they exert on each other are always equal and opposite.

Question 26

Equation to calculate object s momentum

Answer 26

``` Momentum = mass x velocity P = m x v ```

Question 27

Unit used for momentum

Answer 27

Kgm/s | Kilogram meters per seconds

Question 28

In a closed system, what can be said about the momentum before and after a collision?

Answer 28

The total momentum before and after are equal

Question 29

Equation linking change in momentum, force and time

Answer 29

``` Force = change in momentum/time (Mv-mu)/t = F ```

Question 30

How can you measure human reaction times?

Answer 30

Using the ruler drop test Person A and B hold each end of a ruler with 0cm mark at the bottom Person A drops the ruler without telling person B Person B catches it The distance travelled corresponds to their reaction time.

Question 31

Why is it impossible that the 0cm mark is at the bottom?

Answer 31

So you can obtain the distance directly without having to calculate it; otherwise a zero error would need to be accounted for.

Question 32

What is the stopping distance of a vehicle equal to?

Answer 32

The sum of thinking distance and braking distance

Question 33

For a given braking distance , if the vehicle’s speed is increased, what can be said about its stopping distance?

Answer 33

The stopping distance is increased with an increase in speed

Question 34

Typical range of values for human reaction time

Answer 34

0.2 - 0.9 seconds

Question 35

Give three factors which can affect a drivers reaction time

Answer 35

Tiredness Drugs Alcohol

Question 36

Give two factors which may affect braking distance

Answer 36

Adverse (wet/icy) road conditions | Poor tyre/brake conditions

Question 37

Describe energy transfers that take place when a car applies its brakes

Answer 37

Work is done by friction force between the brakes and wheel | Kinetic energy of the wheel is converted to heat and is dissipated to the surroundings through the brake discs

Question 38

To stop a car in given distance, if it’s velocity is increased, what must happen to braking force applied?

Answer 38

The braking force must also be increased

Question 39

State two consequence of a vehicle undergoing very large decelerations

Answer 39

KE converted to heat is very high causing brakes to overheat | Loss of control of the vehicle