Forces and motion

Question 1

How do forces affect an object?

Answer 1

• If the forces acting on an object are balanced, it’s at rest or has a constant speed.
• If the forces acting on an object are unbalanced, it speeds up or slows down.

Question 2

Unit for force

Answer 2

Newtons (N)

Question 3

Word Equation for Force

Answer 3

Force = mass x acceleration

Question 4

Force

Answer 4

F =ma

Question 5

Mass

Answer 5

in kg

Question 6

Reaction time, and therefore thinking distance, may increase if a driver is:

Answer 6

• Tired
• Under the influence of alcohol or other drugs
• Travelling faster
• Distracted or lacks concentration

Question 7

Braking distance may increase if:

Answer 7

• The road conditions are poor e.g. icy
• The car has not been properly maintaned e.g. worn tires.
• The speed is increased.

Question 8

For safe driving, it is important to be able to stop safely:

Answer 8

• Keep an appropiate distance from the car in front.
• Have different speed limits for different types of roads and locations.
• Slow down when road conditions are poor.

Question 9

Factors that affect braking distance are:

Answer 9

• The greater the mass or speed of a vehicle the greater its braking distance.
• When the brakes are applied the brake pads are pushed against the disc. This creates a large friction force that slows the car down. Worn brakes reduce the friction force, increasing the braking distance.
• Worn tyres with very little tread reduce the grip of the wheels on a slippery road, leading to skidding and an increase in braking distance.
• Increased braking force reduces the stopping distance.

Question 10

How does thinking and braking distance increase?

Answer 10

• Thinking distance increases linearly with speed.
• Braking distance increases as a squared relationship. E.g. the braking distance at 60 mph is nine times the braking distance of 20 mph,