Road Science

Question 1

What Is Average Speed?

Answer 1

Speed is the rate at which an object changes its distance with time.

Question 2

What Is The Formula To Determine The Average Speed?

Answer 2

Average speed = total distance ÷ time travelled. Or Vav = d ÷ t

Question 3

What Is Velocity?

Answer 3

Velocity is the rate at which an object changes its distance with time and has a direction. For example, 400km North.

Question 4

How Do You Convert Units Of Speed Between KM/H and M/S?

Answer 4

M/S to KM/H (x 3.6)
KM/H to M/S (÷ 3.6)

Question 5

What Is Instantaneous Speed?

Answer 5

Instantaneous speed is the speed at a particular instant in time.

Question 6

How Do You Calculate The Instantaneous Speed From The Slope Of A Distance-Time Graph?

Answer 6

When the slope on a distance-time graph is steeper, the speed is greater. By drawing a tangent to the curve, you can use d ÷ t = v

Question 7

What Is Acceleration?

Answer 7

Acceleration is the rate at which an object changes its velocity with time.

Question 8

What Is The Acceleration Formula For An Object That Isn’t Changing Directions?

Answer 8

Average Acceleration = change in speed ÷ time taken

aav = (v-u) ÷ t

(This has to be in m/s squared)

Question 9

How Can You Find The Instantaneous Acceleration Of An Object That Isn’t Changing Its Direction?

Answer 9

It can be found from the slope of a speed-time graph.

Question 10

What Is The Formula For Stopping Distance?

Answer 10

Stopping distance = braking distance + reaction distance

Question 11

What Factors Affect Braking Distance?

Answer 11

• Weather conditions (icy, wet, dry)
• Road surface (bitumen, gravel, dirt)
• Tyre conditions (treaded, bald, slick)
• Quality of brakes (new, worn)
• Speed

Question 12

What Factors Affect Reaction Distance?

Answer 12

• Alcohol
• Drugs
• Speed
• Alertness/ sleepiness

Question 13

What Is Reaction Distance?

Answer 13

Reaction distance is the distance covered during the reaction time. (From noticing the stimulus, to putting your foot on the brake - reacting to it).

Question 14

What Is Braking Distance?

Answer 14

Braking distance is the distance covered during the braking time. (From putting your foot on the brake to coming to a complete stop/ colliding with the object).

Question 15

What Does A Straight Line Of A V-T Graph Represent?

Answer 15

It represents constant acceleration/ deceleration.

Question 16

What Does A Curved Line Of A D-T Graph Represent?

Answer 16

It represents acceleration/ deceleration (not constant).

Question 17

What Does A Straight Line Of A D-T Graph Represent?

Answer 17

It represents constant speed.

Question 18

What Does A Horizontal Line Of A D-T Graph Represent?

Answer 18

It represents no speed/ stopped.

Question 19

What Does A Horizontal Line Of A V-T Graph Represent?

Answer 19

It represents constant speed but no acceleration.

Question 20

What Does A Curved Line Of A V-T Graph Represent?

Answer 20

It represents increasing acceleration. This is because the acceleration isn’t constant (a straight line).

Question 21

Can You Be Accelerating If You’re Not Changing Speed Or Direction?

Answer 21

No, you can’t. However, when something slows down, it will have acceleration, because this is a change in speed.

Question 22

What Is Newton’s First Law Of Motion?

Answer 22

Newton’s first law of motion states that an object remains at rest, or continues to move in a straight line, at a constant speed, unless acted upon by an unbalanced force.

Question 23

What Is Inertia?

Answer 23

Inertia is an object’s tendency to remain at rest or continue moving in its current state of motion.

Question 24

What Is Newton’s Second Law?

Answer 24

The acceleration of an object is directly proportional to the total force acting on it, and inversely proportional to its mass. The direction of the acceleration is the same as the direction of the total force.

Question 25

Using Newton’s Laws Why Do Cars Have Head Rests?

Answer 25

During rear end collisions, the car moves forwards and the seat pushes the occupant’s body along with it. Without the head rest, the occupant’s head with remain at rest (according to Newton’s First Law) while the rest of the body is moved forward, possibly causing whiplash. Headrests provide an unbalanced force to support and accelerate the head at the same rate as the body, preventing whiplash.

Question 26

Using Newton’s Laws Why Do Cars Have Restraining Barriers?

Answer 26

Restraining barriers, such as those between the boot compartment and the back seat, provide an unbalanced force, preventing items in the boot from continuing travelling in a straight line at a constant speed when a collision occurs, possibly impacting the occupant and causing injury.

Question 27

Using Newton’s Laws Why Do Cars Have Crumple Zones?

Answer 27

Crumple zones act to increase the time taken for the car to stop when involved in a collision and so decreases acceleration. This decreases the force acting upon the car, and thus the occupants, reducing the chance of serious injury. (The acceleration, or deceleration, is proportional to the force acting, according to F = ma).

Question 28

Using Newton’s Laws Why Do Cars Have Seat Belts?

Answer 28

During a collision, the car stops suddenly, and if unrestrained, the occupant will continue to move in a straight line at a constant speed (according to Newton’s First Law) which could cause injury or death for the occupant. Seat belts provide an unbalanced force, slowing the occupant down with the car, and preventing injury.

Question 29

Using Newton’s Laws Why Do Cars Have Air Bags?

Answer 29

Airbags act to increase the time it takes to stop and so decrease acceleration. This means that the force acting on the person is less than if they had hit a rigid steering wheel. (The acceleration is proportional to the force acting on an object according to F = ma).