P3 to a C grade

Question 1

What factors increase braking distance?

Answer 1

The factors that increase braking distance are slippery road (icey or wet), worn tyres or worn brakes.

Question 2

What happens to kinetic energy if:

(a) the mass is doubled?
(b) the speed is doubled?

Answer 2

KE = 1/2 mv² so

(a) KE doubles
(b) KE quadruples

Question 3

Explain why stopping distance are important in road safety.

Answer 3

Knowing how far the car needs to stop will prevent you crashing into the back of the car in front.

Question 4

Describe arguments for and against electric cars.

Answer 4

For: no pollution from vehicle, quiet.

Against: shorter range, possible pollution from power station producing electricity for recharging, cost.

Question 5

What is power measured in?

Answer 5

Power is measured in Watts. 1 Watt = 1 Joule per second.

Question 6

A force of 75N is applied to a box with a mass of 15kg. What acceleration does this produce?

Answer 6

F = ma, so a = F/m, which gives 75/15 = 5m/s2.

Question 7

What is meant by Work Done?

Answer 7

Work Done is the energy transferred when a force acts over a certain distance.

Question 8

What is the standard unit for speed?

Answer 8

The standard unit for speed is metres per second, m/s

Question 9

A car has a mass of 1000kg and a speed of 10m/s. What is its kinetic energy?

Answer 9

KE = 1/2 mv²

KE = 1/2 x 1000 x 10²

= 50,000J

Question 10

Which tax band would a car emitting 180g of CO₂ per km fall into?

Answer 10

The car will fall into band I which is 220 per year.

Question 11

What factors increase thinking distance?

Answer 11

Thinking distance is increased by faster speed, tiredness, alcohol/drugs and distractions e.g. mobile phones.

Question 12

What do the letters mean in F = ma?

Answer 12

F is force, m is mass and a is acceleration.

Question 13

A crane does 15,000J of work in 30 seconds. What is its power?

Answer 13

Power = work done/time taken

15,000/30 = 500W

Question 14

When a skydiver opens their parachute they slow down. Why is this?

Answer 14

When a skydiver opens their parachute they slow down because the parachute increases their surface area and their air resistance increases so the forces on them are unbalanced.

Question 15

If someone runs at 3m/s for 30 seconds, what distance do they cover?

Answer 15

s = d/t,

d = s x t

distance = 3 x 30 = 90m.

Question 16

What is the law of conservation of energy?

Answer 16

The law of conservation of energy says that enegy cannot be created or destroyed but only changed from one form into another.

Question 17

If a car starts at rest and reaches 25m/s in 10 seconds, what is its acceleration?

Answer 17

a = change in speed/time so, a = 25/10 = 2.5 m/s2

Question 18

What is acceleration?

Answer 18

Acceleration is a measurement of how quickly something’s speed is changing.

Question 19

What is stopping distance?

Answer 19

Stopping distance -= thinking distance + braking distance.

Question 20

Rearrange:

work done = force x distance

so that it is:

force =

Answer 20

You should get:

force = work done/distance.

Question 21

What 2 kinds of energy are exchanged when on a rollercoaster?

Answer 21

When on a rollercoaster the 2 kinds of energy are exchanged are kinetic energy (KE) and gravitational potential energy (GPE). A little energy is lost as sound and heat along the way.

Question 22

What is meant by Power

Answer 22

Power is a measuremnet of how quickly work is done. The faster you do work, or transfer energy, the greater your power.

Question 23

How would you calculate speed from a distance/time graph?

Answer 23

The gradient of the distance time graphs tells us the speed. The steeper the line, the higher the speed.

Question 24

If g = 10 m/s² and someone has a mass of 75kg, what is their weight?

Answer 24

As weight = mass x gravity

weight = 75 x 10 = 750 N.

Question 25

What is thinking distance?

Answer 25

Thinking distance is the distance you travel while you're reacting. It is your speed x your reaction time.

Question 26

How would you calculate acceleration from a speed/time graph?

Answer 26

The gradient of the speed time graphs tells us the acceleration. The steeper the line, the greater the acceleration.

Question 27

What distance is covered during the journey on this speed time graph?

Answer 27

Distance = area under the line, so area of triangle = (8 x 4)/2 = 16 area of rectangle = 8 x 6 = 48 giving a total of 16 + 48 = 64m.

Question 28

How would you calculate distance travelled from a speed/time graph?

Answer 28

The area under a speed time graph tells us the distance travelled. Can you work out why th distance travelled her is 42 m?

Question 29

Which line A or B, represents the higher speed?

Answer 29

It's B because it has a steeper gradient.

Question 30

What forces are experienced by a skydiver?

Answer 30

A skydiver feels the force of gravity (or weight) downwards and air resistance (or drag) up wards.

Question 31

What is speed?

Answer 31

Speed is a measurement of how much distance something travels in a certain time.

Question 32

What is the unit for acceleration?

Answer 32

The unit for acceleration is metres per second per second, or m/s²

Question 33

If C is travelling at 20m/s and D is travelling at 5m/s, how fast is D travelling relative to C?

Answer 33

Viewed from C, D will appear to be moving at 20 + 5 = 25m/s.

Question 34

What is braking distance?

Answer 34

Braking distance is the distance you travel once you've put your foot on the brakes.

Question 35

Why might a 2.0 litre car engine cause more environmental damage than a 1.4 litre car engine?

Answer 35

A larger engine will burn more fuel and release more carbon dioxide into the atmosphere.

Question 36

What can you say about the forces on a skydiver when they reach terminal velocity?

Answer 36

When the skydiver reaches terminal velocity the forces on them are balanced (equal and opposite)