Energy Transformation and Transfer Quiz

A coolie carrying a heavy box on his head and walking on a straight path does no work on the box. Which statement best explains why?

1. The box is too heavy for the coolie to move.
2. The force applied by the coolie is too small to cause motion.
3. The coolie is moving too slowly to perform work.
4. The force applied by the coolie is in a different direction from the movement.

Answer: (d) The force applied by the coolie is in a different direction from the movement.

A climber lifts a backpack of mass 8 kg to a height of 12 m while climbing a mountain. What will happen to the backpack’s energy if he accidentally drops it?

1. Its potential energy will stay the same.
2. Both potential and kinetic energy will disappear.
3. Its kinetic energy will disappear as soon as it starts falling.
4. Its potential energy will convert into kinetic energy as it falls.

Answer: (d) Its potential energy will convert into kinetic energy as it falls.

A pendulum swings from its highest point to its lowest point. What happens to the energy at the lowest point?

1. Potential energy is maximum at the lowest point
2. Kinetic energy is minimum at the lowest point
3. Potential energy is converted into maximum kinetic energy at the lowest point
4. Both potential and kinetic energy are zero at the lowest point

Answer: (c) Potential energy is converted into maximum kinetic energy at the lowest point

A student places two identical metal plates, one painted black and the other white, under a lamp. After 10 minutes, which plate will feel hotter?

1. The white plate
2. The black plate
3. Both absorb the same amount of heat
4. Neither plate absorbs heat

Answer: (b) The black plate

A pot of water is heated on a stove. Which of the following statements best describes the energy transfer inside the water?

1. Heat moves through the water by conduction only.
2. Hot water rises and cooler water sinks, creating convection currents.
3. Radiation from the pot heats the surrounding air only.
4. The water does not transfer heat within itself.

Answer: (b) Hot water rises and cooler water sinks, creating convection currents.

A scientist is designing a thermos to keep liquids hot for a long time. He has the following materials: 1. A plastic inner layer 2. A metal outer layer 3. A vacuum between the two layers Which combination of energy transfer methods does the vacuum help to prevent?

1. Conduction and convection
2. Radiation and conduction
3. Only radiation
4. Only convection

Answer: (a) Conduction and convection

A student lifts a book from the floor to a height of 2 m. Which type of energy transfer takes place, and how does the book store this energy?

1. Chemical to Thermal; the book gets warmer
2. Mechanical to Potential; the book stores energy due to height
3. Electrical to Kinetic; the book moves faster as it rises
4. Kinetic to Chemical; the book absorbs energy for later use

Answer: (b) Mechanical to Potential; the book stores energy due to height

A boulder of mass 5 kg falls from a height of 70 m. What will be its kinetic energy just before it hits the ground?

1. 2500 J
2. 3000 J
3. 3500 J
4. 4000 J

Answer: (c) 3500 J

A roller coaster starts from rest at the top of a 45 m high track. Assuming negligible friction, what will be its speed at the lowest point? (Take g = 10 m/s²)

1. 30 m/s
2. 45 m/s
3. 50 m/s
4. 900 m/s

Answer: (a) 30 m/s

A metal sphere and a wooden sphere of equal size are dropped from the same height. The mass of the metal sphere is four times the mass of the wooden sphere. Which of the following statements is correct about their kinetic energies just before hitting the ground?

1. Both have the same kinetic energy
2. The metal sphere has four times the kinetic energy of the wooden sphere
3. The wooden sphere has twice the kinetic energy of the metal sphere
4. The kinetic energy of the metal sphere is sixteen times that of the wooden sphere

Answer: (b) The metal sphere has four times the kinetic energy of the wooden sphere