Gravity & weight

Figure 1 shows a floating hot air balloon attached to the ground by a rope.

The hot air balloon is stationary.

The wind is exerting a force on the hot air balloon in Figure 1.

Which arrow shows the direction of the force of the wind in Figure 1 ?

Tick (✓) one box.

Which force causes the hot air balloon to float?

Tick (✓) one box.

Air resistance

Gravity

Upthrust

The hot air balloon in Figure 1 is stationary.

What is the resultant force on the balloon?

Tick (✓) one box.

The resultant force is the tension in the rope.

The resultant force is the weight.

The resultant force is zero.

The mass of the hot air balloon is 350 kg.

Calculate the weight of the hot air balloon.

gravitational field strength = 9.8 N/kg

Use the equation:

_ weight = mass × gravitational field strength

The hot air balloon exerts a force of 200 N on the rope.

The force causes the rope to stretch by 1.60 m.

The rope behaves like a spring.

Calculate the spring constant of the rope.

Use the equation:

Choose the unit from the box.

A skydiver jumped out of a helicopter.

Figure 4 shows a distance–time graph for the first 12 seconds of the skydiver’s fall.

How does Figure 4 show that the speed of the skydiver increased between 1 second and 6 seconds?

Tick (✓) one box.

The gradient decreases

The gradient stays the same

The gradient increases

What happened to the speed of the skydiver between 8 seconds and 12 seconds?

Use Figure 4.

Tick (✓) one box.

The speed decreased

The speed stayed the same

The speed increased

Determine the mean speed of the skydiver between 0 seconds and 12 seconds.

Use Figure 4 and the equation:

The forces acting on the skydiver during the fall were weight and air resistance.

What happened to the weight of the skydiver during the fall?

Tick (✓) one box.

Weight decreased

Weight stayed the same

Weight increased

What happened to the air resistance acting on the skydiver as the speed of the skydiver increased?

Tick (✓) one box.

Air resistance decreased

Air resistance stayed the same

Air resistance increased

The skydiver reached terminal velocity.

How did the forces acting on the skydiver compare at terminal velocity?

Tick (✓) one box.

Which of the following shows the velocity–time graph for the skydiver falling at terminal velocity?

Tick (✓) one box.

The skydiver decelerated when the parachute opened.

The initial resultant force on the skydiver was 960 N.

The mass of the skydiver was 64 kg.

Calculate the initial deceleration of the skydiver.

Use the equation:

Choose the unit from the box.

Figure 11 shows a floating hot air balloon attached to the ground by a rope.

The hot air balloon is stationary.

The wind is exerting a force on the hot air balloon in Figure 11.

Which direction is the force of the wind acting?

What is the name of the upwards force on the hot air balloon?

The weight of the hot air balloon is 3.43 kN.

gravitational field strength = 9.8 N/kg

Calculate the mass of the hot air balloon.

Use the Physics Equations Sheet.

The resultant force on the balloon is zero.

What is meant by ‘resultant force’?

Figure 12 shows a vector diagram of the force of the rope on the hot air balloon.

Scale 1 cm = 50 N

Complete the vector diagram to determine the magnitude of the horizontal and vertical components of the force.

The stopping distance of a vehicle depends on the thinking distance and the braking distance.

What is meant by ‘thinking distance’?

Tick (✓) one box.

The distance travelled before a vehicle stops.

The distance travelled while the driver reacts.

The time taken for a driver to react.

The time taken for the vehicle to stop.

What would increase the braking distance of a vehicle?

Tick (✓) one box.

Ice on the road surface

Sunny weather

Using a mobile phone while driving

What is the name of the force which causes the vehicle to decelerate when the brakes are applied?

Tick (✓) one box.

Friction

Upthrust

Weight

Figure 1 shows how the braking distance of two cars varies with speed.

How does the braking distance of the two cars vary with speed?

Tick (✓) one box.

The braking distance decreases as speed increases.

The braking distance is not affected by speed.

The braking distance increases as speed increases.

To make a fair comparison between the braking distance of the two cars, the mass of each car was the same.

Calculate the weight of a car.

mass = 850 kg

gravitational field strength = 9.8 N/kg

Use the equation:

weight = mass × gravitational field strength

Choose the unit from the box.

Which two variables should be kept the same to make a fair comparison of the braking distance of the two cars?

Tick (✓) two boxes.

The age of the driver

The caffeine intake of the driver

The colour of the car

The number of people in the car

The type of road surface

Table 1 shows the braking force on each car at a speed of 31 m/s.

The braking distance of car A was longer than the braking distance of car B at a speed of 31 m/s.

Explain why.

Use data from Table 1.

The stopping distance of a vehicle depends on the thinking distance and the braking distance.

What is meant by ‘braking distance’?

The braking distance of a vehicle depends on the mass of the vehicle.

Use the Physics Equations Sheet to answer questions 09.2 and 09.3.

Write down the equation which links gravitational field strength (g), mass (m) and weight (W).

Calculate the mass of a vehicle with a weight of 14 700 N.

gravitational field strength = 9.8 N/kg

The thinking distance travelled by a vehicle depends on the reaction time of the driver.

Using a mobile phone increases a driver’s reaction time.

A mobile phone can be used in these ways:

typing a text message

making a phone call while holding the phone

making a hands-free phone call using the car’s audio system.

Figure 21 shows how different activities using a mobile phone affect a driver’s reaction time.

Typing a text Making a hand-held Making a hands-free message
phone call
phone call

Phone activity

The reaction time of a typical driver is 0.50 s.

Calculate the reaction time of a typical driver typing a text message while driving.

The legal alcohol limit is the maximum amount of alcohol a person can have in the bloodstream and still legally drive.

The reaction time of a typical driver at the legal alcohol limit is increased by 12%.

A student suggests that it should be illegal to use a mobile phone in any way while driving.

Explain how the information in Figure 21 supports the student’s suggestion.

The stopping distance of a vehicle depends on the thinking distance and the braking distance.

What is meant by ‘braking distance’?

The braking distance of a vehicle depends on the mass of the vehicle.

Use the Physics Equations Sheet to answer questions 01.2 and 01.3.

Write down the equation which links gravitational field strength (g), mass (m) and weight (W).

Calculate the mass of a vehicle with a weight of 14 700 N.

gravitational field strength = 9.8 N/kg

The thinking distance travelled by a vehicle depends on the reaction time of the driver.

Using a mobile phone increases a driver’s reaction time.

A mobile phone can be used in these ways:

typing a text message

making a phone call while holding the phone

making a hands-free phone call using the car’s audio system.

Figure 1 shows how different activities using a mobile phone affect a driver’s reaction time.

The reaction time of a typical driver is 0.50 s.

Calculate the reaction time of a typical driver typing a text message while driving.

The legal alcohol limit is the maximum amount of alcohol a person can have in the bloodstream and still legally drive.

The reaction time of a typical driver at the legal alcohol limit is increased by 12%.

A student suggests that it should be illegal to use a mobile phone in any way while driving.

Explain how the information in Figure 1 supports the student’s suggestion.

Figure 1 shows a boat pulling a person parasailing.

A rope attaches the person to the boat.

What type of force is the weight?

Tick (✓) one box.

Contact force

Magnetic force

Non-contact force

The mass of the person is 75 kg.

Calculate the weight of the person.

gravitational field strength = 9.8 N/kg

Use the equation:

weight = mass × gravitational field strength

The resultant force acting on the person is zero.

Which of the following describes the motion of the person?

Tick (✓) one box.

Velocity decreasing

Moving at constant velocity

Velocity increasing

The horizontal force on the person is 4300 N.

Calculate the work done by this force in moving the person a horizontal distance of 500 m.

Use the equation:

work done = force × distance

Choose the unit from the box.

The speed of the boat changes.

The height of the person above the water decreases by 18 m.

Calculate the decrease in gravitational potential energy of the person.

mass of person = 75 kg

gravitational field strength = 9.8 N/kg

Use the equation:

gravitational potential energy = mass × gravitational field strength × height

Figure 7 shows a boat pulling a person parasailing.

Figure 7 is not drawn to scale.

Write down the equation which links gravitational field strength (g), mass (m) and weight (W).

The weight of the person is 735 N.

Calculate the mass of the person.

gravitational field strength = 9.8 N/kg

The person is moving at a constant velocity.

What is the resultant force acting on the person?

The magnitude of the force of the rope on the person is 5000 N.

Draw a vector diagram on Figure 8 to determine the vertical component and the horizontal component of the force on the rope.

Figure 8

The force of the rope on the person parasailing is 5000 N.

The boat pulls the person for a horizontal distance of 1000 m.

The work done by the force of the rope on the person is not calculated by multiplying 5000 N by 1000 m.

Explain how the work done by the force of the rope on the person could be calculated.

Figure 5 shows a car travelling at a constant speed on a straight, level road.

Draw an arrow on Figure 5 to show the direction of the force of air resistance on the car.

The mass of the car is 850 kg

Calculate the weight of the car.

Use the equation:

weight = mass × gravitational field strength

gravitational field strength = 9.8 N/kg

What is the direction of the normal contact force of the road on the wheels?

Tick (✓) one box.

The car is travelling at constant speed.

The resultant force on the car is zero.

How does the size of the normal contact force of the road on the wheels compare with the weight of the car?

Tick (✓) one box.

A car is travelling at a constant speed.

A constant braking force of 5100 N is applied by the brakes.

The car decelerates and stops.

The braking distance is 38 m

Calculate the work done by the braking force.

Choose the unit from the box.

Use the equation: work done = force × distance

Which two factors affect braking distance?

Tick (✓) two boxes.

The distance a car travels during the driver’s reaction time is called the thinking distance.

Which factor affects thinking distance?

Tick (✓) one box.

Figure 6 shows a sketch graph of how thinking distance varies with speed.

Which term describes the relationship between thinking distance and speed?

Tick (✓) one box.