Forces in Action (OCR GCSE Physics A (Gateway))

A boy of mass 70 kg stands on the end of a diving board at a distance of 1.8 m from the wall.

Calculate the moment of the boy standing on the diving board.

Gravitational field strength on Earth = 10 N/kg.

Moment = .................................................. N m

The boy dives vertically into the swimming pool. The water in the pool is 3.2 m below the diving board.

Calculate the velocity of the boy when he enters the water.

Use an equation from the data sheet to help you.

Gravitational field strength on Earth = 10 N/kg.

Velocity = ................................................. m/s

A car has a total weight of 12 000 N. It has four tyres which each have an area of 25 cm² in contact with the road.

Calculate the pressure of the car on the road.

Answer = ......................... N/cm²

Seatbelts in cars are made of a wide material that stretches in a crash.

i) Explain why it is important that the material is wide.

[1]

ii) Explain why it is important that the material is stretchy.

[1]

Children in cars use special seats with their own seatbelts.

The seatbelts for children are narrower than adult seatbelts.

Why is it safe for children’s seatbelts to be narrower than adult seatbelts?

Rockets carry satellites into space.

Satellites are kept in orbit around a planet by a force.

State the name of this force.

State the name of the Earth’s natural satellite.

A vehicle called the Mars Rover was sent to Mars in a rocket.

The Mars Rover has a mass of 185 kg. The gravitational field strength (g) on Mars is 3.75 N/kg.

Calculate the weight of the Mars Rover vehicle on Mars.

State the unit for weight.

Show your working and give your answer to 3 significant figures.

 Answer = ......................... Unit = ..........

Explain why the Mars Rover weighs more on Earth than on Mars.

Two gears, A and B, are shown in Fig. 1.1.

Fig. 1.1

Gear A has 10 teeth and gear B has 50 teeth. Both gears have the same size teeth.

Gear B moves in a clockwise direction and rotates at a rate of 4 revolutions per minute.

(i) What is the direction of rotation of gear A? Put a ring around the correct option.

clockwise‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ anticlockwise

(ii) How many revolutions are completed by gear A in one minute?

Number of revolutions = ....................................... per minute

Fig. 1.2 shows two gears, B and C, where gear C can move up or down.

Fig. 1.2

The distance between each of the teeth on gear B and gear C is 2 mm.

Gear C moves downward at a rate of 200 mm per minute.

(i) What is the direction of rotation of gear B? Put a ring around the correct option.

clockwise‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ ‎ anticlockwise

(ii) How many revolutions are completed by gear B in one minute?

Number of revolutions = ....................................... per minute

Fig 1.3 shows an experiment set up by a student to study moments.

Fig 1.3

The student hangs the rod from the ceiling by tying a string to the centre of the rod.

They then add three weights to the rod at different distances from the string until the system is in equilibrium.

Calculate the mass in g of the weight on the right end of the rod.

Use the equation: moment of a force = force × distance