P3: Forces for Transport

Question 1

What are the 3 main measurements for speed?

Answer 1

Metres per Second (m/s)
Kilometres per Hour (km/h)
Miles per Hour (mph)

Question 2

How do you measure the speed of an object?

Answer 2

Speed (m/s) = Distance Travelled (m) divided by Time Taken (s)

Question 3

How do you work out distance and average speed?

Answer 3

For an object that is changing speed it is possible to calculate the distance it travels by using the average speed:

Distance = Average Speed x Time

Distance = (u + v) divided by 2 x t
(Where u is the starting speed and v is the final speed)

Question 4

How do you work out acceleration or deceleration of an object?

Answer 4

Acceleration (or deceleration) (m/s squared) = Change in speed (m/s) divided by Time taken for change (s)

Question 5

What are forces?

Answer 5

Forces are push and pulls measured in Newtons (N) and may be different in size and act in different directions.

Forces can cause objects to speed up or slow down, for example:
Gravity causes an apple falling from a tree to speed up as it falls; it accelerates.
Friction causes a car to slow down; it decelerates.
Air resistance causes a parachutist to slow down after opening a parachute; she decelerates.

Question 6

The relationship between force, mass and acceleration are shown how?

Answer 6

Force (N) = Mass (kg) x Acceleration (m/s squared)

Question 7

What does the stopping distance of a vehicle depend on?

Answer 7

Thinking Distance and braking distance.
(Stopping Distance = Thinking Distance + Braking Distance)

But may also depend on vehicle speed, road condition, vehicle condition (e.g. Brakes), etc.

Question 8

Energy is needed to work. Both energy and work are measured in what?

Answer 8

Joules (J)

Work done (J) = Energy Transferred (J)

The amount of work depends on the size of the force in newtons and the distance the object is moved in metres in the direction of the force. (Work Done (J) = Force (N) x Distance (m)

Question 9

If you are lifting you own weight, you are doing work. What is the formula for this?

Answer 9

Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg)

Question 10

What is the formula for working out how power you have used?

Answer 10

Power (W) = Work done (J) divided by Time (s)

Question 11

How do you calculate kinetic energy?

Answer 11

Kinetic Energy (J) = 1/2 x Mass (kg) x Speed squared (m/s) squared (Meaning Speed² (m/s)²)

Question 12

How is momentum calculated?

Answer 12

Momentum (kg m/s) = Mass (kg) x Velocity (m/s)

Question 13

How can force be calculated?

Answer 13

Force (N) = Change of momentum (kg m/s) divided by Time (s)