Module 3 Chapter 1 Motion

Question 1

In the suvat equations, what does s denote?

Answer 1

Displacement (m)

Question 2

In the suvat equations, what does u denote?

Answer 2

Initial Velocity (m s-1)

Question 3

In the suvat equations, what does v denote?

Answer 3

Final Velocity (m s-1)

Question 4

In the suvat equations, what does a denote?

Answer 4

Acceleration (m s-2)

Question 5

In the suvat equations, what does t denote?

Answer 5

Time (s)

Question 6

What equation would you use to find final velocity given initial velocity, acceleration and time?

Answer 6

v = u + a*t

Question 7

What equation would you use to find final velocity given initial velocity, acceleration and displacement?

Answer 7

v^2 = u^2 + 2as

Question 8

What equation would you use to find displacement given initial velocity, final velocity and time?

Answer 8

s = 1/2(u + v)t

Question 9

What equation would you use to find displacement given initial velocity, acceleration and time?

Answer 9

s = ut + 1/2a*t^2

Question 10

Rearrange v = u + a*t for u

Answer 10

u = v - a*t

Question 11

Rearrange v = u + a*t for a

Answer 11

a = (v - u)/t

Question 12

Rearrange v = u + a*t for t

Answer 12

t = (v - u)/a

Question 13

Rearrange v^2 = u^2 + 2as for u^2

Answer 13

u^2 = v^2 - 2as

Question 14

Rearrange v^2 = u^2 + 2as for a

Answer 14

a = (v^2 - u^2)/(2*s)

Question 15

Rearrange v^2 = u^2 + 2as for s

Answer 15

s = (v^2 - u^2)/(2*a)

Question 16

Rearrange s = 1/2(u + v)t for u

Answer 16

u = (s/t)*2 - v

Question 17

Rearrange s = 1/2(u + v)t for v

Answer 17

v = (s/t)*2 - u

Question 18

Rearrange s = 1/2(u + v)t for t

Answer 18

t = (2*s)/(u + v)

Question 19

Rearrange s = ut + 1/2a*t^2 for u

Answer 19

u = (s - 1/2at^2)/t

Question 20

Rearrange s = ut + 1/2a*t^2 for a

Answer 20

a = 2(s - ut)/t^2

Question 21

Rearrange s = ut + 1/2a*t^2 for t

Answer 21

t = ((2as + u^2)^(1/2) - u)/a

Question 22

What is kinematics?

Answer 22

The study of the motion of objects and their spacial relationships, without any reference to either their mass or the forces that cause them to change direction or speed.

Question 23

What are the key quantities used in kinematics?

Answer 23

• Speed
• Displacement
• Velocity
• Acceleration

Question 24

Define speed.

Answer 24

Distance per unit time.

Question 25

What are the units for speed?

Answer 25

m s-1 or km h-1

Question 26

Define displacement.

Answer 26

Distance moved in a particular direction from a reference point.

Question 27

What are the units for displacement?

Answer 27

m or km

Question 28

Define velocity.

Answer 28

Displacement per unit time.

Question 29

What are the units for velocity?

Answer 29

m s-1 or km h-1

Question 30

Define acceleration.

Answer 30

Change in velocity per unit time.

Question 31

What are the units for acceleration?

Answer 31

m s-2

Question 32

Why do objects of different masses fall at the same rate?

Answer 32

Because while a larger mass means a greater force is acting on the object (F = m*a), acceleration is reduced by the increase in mass (a = F/m). These changes are equal in magnitude and therefore cancel each other out.

Question 33

Why do feathers fall slower than bricks?

Answer 33

Because they have a much larger surface area to mass ratio and so air-resistance has a much greater impact, giving the feather a much lower terminal velocity. In a vacuum, they would fall at the same rate.

Question 34

In F = m*g, what does g denote?

Answer 34

Gravitational field strength, or acceleration due to gravity, 9.81 m s-1 on Earth.

Question 35

What is the acceleration of an object that has been thrown vertically upwards?

Answer 35

-g or -9.81 m s-1
(on Earth)
This is because once the object has been released, there is no force acting upwards on it, just the force of gravity which counteracts the object’s initial velocity, from being thrown upwards, at the rate of 9.81 m s-1.

Question 36

If you threw a ball vertically upwards in a vacuum with an initial velocity of 37.8 m s-1, what would the velocity of the ball be the instant before it stopped, assuming you catch it at exactly the same height you released it from?

Answer 36

37.8 m s-1
because it travels the same distance down as it does up, accelerating at the same rate on its way down as it decelerated on the way up.

Question 37

What effect does vertical motion have on horizontal motion?

Answer 37

None. They are independent.

Question 38

What effect does horizontal motion have on vertical motion?

Answer 38

None. They are independent.

Question 39

What shape does the path of an object shot from the ground at a 45 degree angle in a vacuum form?

Answer 39

A symmetrical arc.

Question 40

In the absence of air resistance, at what rate does a projectiles horizontal velocity decrease?

Answer 40

0 m s-1

Question 41

What is the stopping distance of a vehicle?

Answer 41

The distance traveled by a vehicle between the driver seeing an obstacle and the vehicle coming to a complete stop.

stopping distance = thinking distance + braking distance

Question 42

What is thinking distance?

Answer 42

The distance a vehicle travels between the driver seeing the hazard and applying the brakes.

Question 43

What is braking distance?

Answer 43

The distance the vehicle travels between the driver applying the brakes and coming to a rest.

Question 44

List five factors that increase thinking distance.

Answer 44

• Higher speed
• Tiredness
• Alcohol and drugs (not all drugs)
• Distractions
• Age of the driver

Question 45

List five factors that increase braking distance.

Answer 45

• Higher speed
• Poor road conditions
• Poorly maintained brakes
• Poorly maintained tyres
• The mass of the vehicle

Question 46

If speed doubles, how is thinking distance affected?

Answer 46

It doubles.

Question 47

If speed doubles, how is braking distance affected?

Answer 47

It quadruples.

Question 48

If speed triples, how is thinking distance affected?

Answer 48

It triples.

Question 49

If speed triples, how is braking distance affected?

Answer 49

It increases nine-fold.

Question 50

What is the relationship between speed and thinking distance?

Answer 50

speed ∝ thinking distance

Question 51

What is the relationship between speed and braking distance?

Answer 51

speed ∝ braking distance