Energy Work and Power IGCSE

A steel ball is fired vertically upwards with a velocity v. The ball reaches a height h.

The same ball is now fired vertically upwards from the same position with a velocity 2v.

Air resistance can be ignored.

What is the new height reached by the ball?

• h

• 2h

• 4h

• 8h

Tags

NGSS.MS-PS2-4

NGSS.MS-PS3-1

NGSS.MS-PS3-2

A solar panel is used to recharge a battery. The solar panel produces 0.80 W of electrical power.

The panel is 20% efficient.

What is the power input of the sunlight onto the solar panel?

• 0.16 W

• 4.0 W

• 8.0 W

• 16 W

Tags

NGSS.MS-ETS1-1

NGSS.MS-PS3-3

The diagrams show four different athletes training by doing pull-ups.

Which athlete does the most work?

• 
• 
• 
• 

Tags

NGSS.MS-PS3-5

A motor is used to lift a load of 40 N.

The power of the motor is 40 W and the system is 20% efficient.

How long does it take the motor to lift the load through 0.50 m?

• 0.50 s

• 2.5 s

• 5.0 s

• 25 s

Tags

NGSS.MS-PS2-2

A student runs up a flight of stairs.

Which information is not needed to calculate the rate at which the student is doing work against gravity?

• the height of the flight of stairs

• the length of the flight of stairs

• the time taken to run up the stairs

• the weight of the student

The diagrams show athletes training by stretching springs.

Each spring has the same stiffness.

Which athlete does the most work?

• 
• 
• 
• 

Tags

NGSS.MS-PS3-2

An electric generator produces an electromotive force (e.m.f.) of 200 V and produces a current of 3.0 A in a circuit.

The generator is driven by an engine with a power of 2.4 kW.

What is the efficiency of the generator?

• 2.8%

• 25%

• 28%

• 36%

Tags

NGSS.HS-PS3-3

Different processes have different efficiencies.

Which row shows the most efficient process?

• A

• B

• C

• D

Tags

NGSS.MS-ETS1-1

NGSS.MS-ETS1-2

A 150 W filament lamp has an efficiency of 10%. A 40 W compact fluorescent lamp (CFL) has an

efficiency of 30%.

Each lamp is switched on for the same amount of time.

Which lamp produces more light and which lamp converts more energy into other forms of

energy

• A

• B

• C

• D

Tags

NGSS.MS-PS3-4

A lamp has a power input of 5.0 W. It wastes 1.0 W of power heating the surroundings.

What is the efficiency of the lamp?

• 20%

• 50%

• 80%

• 120%