Conservation of Energy (OCR GCSE Physics A (Gateway))

A car on a roller coaster is stationary at the top of a slope.

The car has a weight of 6 500 N and a potential energy of 217 000 J.

Calculate the cars height above the ground.

Answer = ......................... m

The diagram shows the roller coaster car moving down a slope.

The energy at the bottom of the slope is less than expected. Suggest two ways to improve the efficiency of the roller coaster car.

The table shows the stopping distances for a car.

Add the missing results to the table at a speed of 32 m/s.

Higher Tier Only

The car takes 6 m to brake when moving at 8 m/s.

Look at the graph of the car as it starts to brake and then stop.

Use the graph to show that the braking distance is 6 m.

The formula to work out kinetic energy is:    

kinetic energy = 0.5 × mass × (velocity²)

A car has 30 000 J of energy and a mass of 1 tonne (1 tonne = 1 000 kg).

Calculate the velocity of the car and show your working.

Answer = ......................... m/s

Cars and lorries have different brakes.

• Brakes absorb the energy of the vehicle before it comes to rest.

• The brakes on lorries have larger brake discs and brake pads than cars.

• Brakes are designed to increase airflow.

Explain why increased airflow is more important for lorries than cars.

Salmon are born in freshwater rivers, spend most of their lives in the sea, but return to freshwater rivers to breed. As they swim up rivers, they often have to jump up waterfalls.

Fig. 1.1 shows a salmon attempting to jump up a waterfall with a vertical height of 0.36 m.

Fig. 1.1

The salmon has a mass of 1.84 kg.

The salmon leaves the water at a speed of 3.2 m/s.

Determine whether the salmon can make the height required for the jump.

Use the Equation Sheet.

Another salmon of mass 2.2 kg tries to make the jump. 

Calculate the minimum speed with which the salmon would have to leave the water in order to reach the height required.

Use the Equation Sheet.

The salmon swim far upstream and encounter a high waterfall.

 The salmon attempts to jump to the top of the waterfall but fails and performs a somersault during the descent. The salmon straightens out before it enters the water as shown in Fig. 1.2.

Fig 1.2

State whether the speed of entry into the water is greater than, less than, or equal to the speed with which it leaves the water. Give a reason for your answer.

Ignore any effects of air resistance.

The temperature of the water at the bottom of a waterfall is greater than the temperature of the water at the top. 

Suggest why this is the case. 

The diagram shows a student at two stages of a bungee jump.

Complete the following sentences about the bungee jump.

Before the student jumps, the student has energy in their .................. store. As the student falls, energy is transferred to their ................ store.

At the bottom of the jump, the bungee chord stretches, and energy is transferred to the .................... store of the rope.

At the lowest point of the jump, the student is momentarily stationary. At this point, the length of the bungee cord is 82 m. The unstretched length of the cord is 40 m.

The bungee cord acts like a spring with a spring constant of 45 N/m.

Calculate the energy stored in the bungee cord at the lowest point of the jump.

Use the Equation Sheet.

Determine the mass of the student.

You may assume there are no energy losses in the system.

Use the Equation Sheet.

Determine the speed of the student at the point in the jump where the bungee cord is at its maximum unstretched length.

You can assume air resistance is negligible.

Use the Equation Sheet.