Energy Transfer - WS - L21 - PHY

A hiker climbs a hill 300m high. If she has a mass of 50kg, calculate the work she does in lifting her body to the top of the hill.

• 150kJ

• 15kJ

• 150J

• 1.5mJ

In loading a lorry a man lifts boxes each of weight 100N through a height of 1.5m. a. How much work does he do in lifting one box? b. How much energy is transferred when one box is lifted? c. If he lifts four boxes per minute, at what power is he working? (3 Points)

• a = 150J, b = 150J, c = 10W

• a = 150J, b = 300J, c = 2.5W

• a = 15kJ, b = 150J, c = 1W

• a = 150J, b = 75J, c = 5W

An escalator carries 60 people of average mass 70kg to a height of 5m in one minute. Find the power needed to do lift these people.

• 3500W

• 400W

• 26.1W

• 5.8W

When the energy input to a gas-fired power station is 1000 MJ, the electrical energy output is 300 MJ. a. What is the efficiency of the power station in changing the energy in gas into electrical energy? b. What form is the final fate of the 700 MJ of 'lost' energy?

• a = 30%, b = Thermal

• a = 70%, b = Kinetic

• a = 50%, b = Sound

• a = 80%, b = Potential

State the energy transfer that occurs when someone speaks into a microphone

• Sound energy to Electrical energy

• Electrical energy to Sound energy

• Electrical energy to Thermal energy

• Kinetic energy to Potential energy

A boy whose weight is 600N runs up a flight of stairs 10m high in 12s. What is his average power?

• 500W

• 50W

• 120W

• 600W

Name the forms of energy represented by the letters A, B, C and D in the following statement: In a coal-fired power station, the (A) energy of coal becomes (B) energy which changes water into steam. The steam drives a turbine which drives a generator. A generator transfers (C) energy into (D) energy. (4 Points)

• A = Chemical, B = Thermal, C = Kinetic, D = Electrical

• A = Chemical, B = Sound, C = Kinetic, D = Thermal

• A = Potential, B = Thermal, C = Kinetic, D = Nuclear

• A = Chemical, B = Potential, C = Kinetic, D = Radiant

How much work is done when a mass of 3 kg (weighing 30 N) is lifted vertically through 6 m?

• 18J

• 180J

• 9J

• 2J

State the energy transfers which occur when an electric bell rings.

• A) Electrical energy to Sound energy

• B) Electrical energy to Nuclear energy

• C) Electrical energy to Light energy

• D) Chemical energy to Internal energy