Newton's Laws and Forces and Braking

Question 1

What is Newton’s first law?

Answer 1

• if there is no resultant force acting on a stationary object, it will remain stationary
• if there is no resultant force acting on a moving object, then it will continue to move at the same velocity

Question 2

What is inertia?

Answer 2

• tendency of object to stay at rest or continue moving with uniform motion

Question 3

What is Newton’s second law?

Answer 3

• acceleration of an object is proportional to the resultant force acting on the object
• inversely proportional to the mass of the object
• F = m x a

Question 4

What is inertial mass?

Answer 4

• measure of how difficult it is to change the velocity of an object
• ratio of force/ acceleration

Question 5

How do you measure the effect on acceleration when force or mass are changed?

Answer 5

1) measure length of each card segment
2) string should be 0.5-1cm off the floor when trolley is as close to pulley as possible
3) set up data logger to calculate acceleration of trolley
4) add mass to mass holder = 250g
5) pull back trolley, set data logger to record, let trolley go. collect measurement from data logger
6) take 50g off mass holder, repeat 5-6 until 50g left
7) repeat experiment, calculate mean

Question 6

What is Newton’s third law?

Answer 6

• two objects exert equal and opposite forces on each other when they interact

same type of force -> push pull

Question 7

What is the stopping distance of a driven vehicle?

Answer 7

• thinking distance + braking distance

Question 8

What is thinking distance?

Answer 8

• distance vehicle travels while driver is reacting

reaction time

Question 9

What is the braking distance of a car?

Answer 9

• distance vehicle travels after force is applied on brakes

Question 10

What happens to the stoppping distance as speed increases with the same braking force?

Answer 10

• increases
• vehicle travels further in same time

Question 11

What increases reaction time?

Answer 11

• tiredness
• alcohol or drugs
• distractions (eg phone)

Question 12

What increases braking distance?

Answer 12

• wet/ icy road = less friction tyres and surface = travel further whilst braking
• worn out brakes/ tyres = larger force needed, less friction

Question 13

What is the typical range of reaction time?

Answer 13

0.2 - 0.9 s

Question 14

How do you measure reaction time?

Answer 14

• dropping ruler and see how far it falls
• detecting stimulus (sound/ light) and responding to it (button)

0.7 = typical value

Question 15

Describe what happens when force is applied to the brakes of a vehicle

Answer 15

• work done by frction force between brakes + wheel reduces kinetic energy of vehicle
• temperature of brakes increase

Question 16

What are the dangers of large decelerations?

Answer 16

• brakes overheating
• loss of control