4.6.5 Forces and motion (might come up) P2

Question 1

State Newton’s first law for a stationary object

Answer 1

If the resultant force on a stationary object is 0, the object will remain at rest

Question 2

State Newton’s first law for a moving object

Answer 2

If the resultant force on a moving object is zero, the object will remain at constant velocity (same speed same direction)

Question 3

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

Answer 3

The braking forces are equal to the driving forces

Question 4

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

Answer 4

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

Question 5

What is inertia

Answer 5

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

Question 6

State Newton’s second law

Answer 6

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

Question 7

What is inertia mass

Answer 7

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

Question 8

Newton’s third law

Answer 8

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

Question 9

What is the stopping distance of a vehicle equal to

Answer 9

The sum of thinking distance and breaking distance

Question 10

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

Answer 10

The stopping distance is increased with an increase in speed

Question 11

Typical range for human reaction time

Answer 11

0.2-0.9 seconds

Question 12

3 factors which can affect a driver’s reaction time

Answer 12

Tiredness
Drugs
Alcohol

Question 13

2 factors which may affect braking distance

Answer 13

Adverse road conditions (wet/icy)

Poor tyre/brake conditions

Question 14

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

Answer 14

Work is done by the 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 15

To stop a car in a given distance, if its velocity is increases, what must happen to the braking force applied

Answer 15

Braking force must also be increased

Question 16

2 consequences of a vehicle undergoing very large decelerations

Answer 16

Kinetic energy converted to heat is very high causing brakes to overheat
Loss of control of the vehicle