P10: Forces & Motion

Question 1

Does a distance require a specific direction?

Answer 1

No specific direction is required so it is a scalar quantity

Question 2

If an object moves 3 metres to the left and then 3 metres back to its initial position, what is the objecy’s total displacement?

Answer 2

The object has zaero displacement
Displacement is a vector quantity so it also involves direction
The object starts and ends at the same point

Question 3

State a typical value for speed of sound?

Answer 3

330 m/s

Question 4

What is a typical value for human walking speed?

Answer 4

1.5 m/s

Question 5

What is a typical value for human running speed?

Answer 5

3 m/s

Question 6

What is s typical value for human cycling speed?

Answer 6

6 m/s

Question 7

State the equation linking distance, speed and time?

Answer 7

Distance = Speed x Time

Question 8

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

Answer 8

Drawing a tangent to the curve at the required time
Calculating the gradient of the tangent

Question 9

State the equation for the average acceleration of an object. Give appropriate units?

Answer 9

Acceleration = Change in velocity/time taken

Question 10

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

Answer 10

It is equal to the area under the graph

Question 11

What can be siad about the resultant force acting on an object when it is falling at terminal velocity?

Answer 11

The resultant force is zero
When at terminal velocity, the object is moving at a constant speed and so isn’t accelerating

Question 12

State Newton’s first law for a stationary object?

Answer 12

If the resultant force on a stationary object is zero, the object will remain at rest

Question 13

State Newton’s first law for a moving object?

Answer 13

If the resultant force on a moving object is zero, the object will remain at constant velocity

Question 14

What can be said about the braking forces and driving forces when a car is travellin* at constant velocity?

Answer 14

The braking forces are equal to the driving forces

Question 15

If an object changes direction but remains at a constant speed, is there a resultant force?

Answer 15

Since there is a change in direction, there is a change in velocity and so there must be a resultant force

Question 16

What is inertia?

Answer 16

The tendency of an object to continue in its state of rest or uniform motion

Question 17

State the defining equation for Newton’s Second Law?

Answer 17

Resultant force = Mass x acceleration
F =ma

Question 18

State Newton’s second law in words?

Answer 18

An object’s acceleration is directly proportional to the resultant force acting on it and inversely proportional to its mass

Question 19

What is inertial mass?

Answer 19

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

Question 20

State Newton’s Third Law?

Answer 20

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

Question 21

What is the stopping distance of a vehicle equal to?

Answer 21

The sum of thinking distance and braking distance

Question 22

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

Answer 22

The stopping distance in increased wit( an increased in speed

Question 23

Give a typical range of values for human reaction time?

Answer 23

0.2s - 0.9s

Question 24

Give 3 factors which can affect a driver’s reaction time?

Answer 24

Tiredness
Drugs
Alcohol

Question 25

Give 2 factors which may affect braking distance?

Answer 25

Adverse road conditions
Poor tyre conditions

Question 26

State the equation used ro calculate momentum?

Answer 26

Momentum = mass x velocity

Question 27

What is the unit for momentum?

Answer 27

Kg m/s

Question 28

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

Answer 28

The total momentum before is equal to the toatl momentum afterwards

Question 29

State an equation linking change in momentum, force and time?

Answer 29

Force x Time = Change in momentum

Question 30

What quantity is equal to the force experienced in a collision?

Answer 30

The rate of change of momentum

Question 31

If an objectks momentum is foxed, what is the only way to reduce the force that the object experiences?

Answer 31

Increases the length of time over which the change of momentum occurs