Olympiad Test: Work, Force And Energy -2 - Class 4 MCQ

A thermometer is used to measure temperature. It can measure both hot and cold temperatures, typically in degrees Celsius or Fahrenheit.

• Option A (Stopwatch) is used to measure time.
• Option B (Scale) is used to measure weight or mass.
• Option C (Measuring jar) is used to measure the volume of liquids.

Thus, the correct answer is Option D: Thermometer.

A calorimeter is an instrument used to measure the amount of heat absorbed or released during a chemical reaction, physical change, or phase transition. It helps determine how much heat is involved in the process.

• Option A is incorrect because a calorimeter doesn't directly "determine the heat of a reaction" in an abstract sense, but measures the heat transferred.
• Option C is incorrect because a calorimeter doesn't store heat; it measures it.
• Option D is incorrect because Option B is the correct answer.

Thus, the correct answer is Option B: Determine the heat given off/absorbed during some process.

Nuclear energy is the energy stored in the nucleus (core) of an atom. It can be released through processes like fission (splitting atoms) or fusion (combining atoms), which release a large amount of energy. This energy can be harnessed for electricity generation, medicine, and other applications.

• Option A refers to solar energy, which is derived from the sun.
• Option C refers to electrical energy or kinetic energy from moving electrons.
• Option D refers to radiant energy like light, which travels in waves.

Thus, the correct answer is Option B: Energy that is locked in the nucleus of an atom.

As you go up a mountain, your weight decreases slightly because the force of gravity is weaker at higher altitudes. This happens because you are farther away from the Earth's center, where gravity is slightly weaker. However, the change in weight is very small and not noticeable without precise measurement.

Thus, the correct answer is Option B: Decreases slightly.

All the options listed are SI units:

• Watt (Option A) is the SI unit of power.
• Newton (Option B) is the SI unit of force.
• Joule (Option C) is the SI unit of energy.

Since all the listed units are part of the International System of Units (SI), the correct answer is Option D: none.

Headphones contain an electromagnet as part of the speaker mechanism that converts electrical signals into sound.

• Option A (Lamp) generally does not contain an electromagnet.
• Option B (Electric stove) uses electrical heating elements but not an electromagnet.
• Option C (Compass) uses a magnetic needle, but it does not rely on an electromagnet.

Thus, the correct answer is Option D: Headphones.

The mechanical energy of a freely falling object is the sum of its kinetic energy and potential energy. As the object falls, its potential energy decreases, and its kinetic energy increases, but the total mechanical energy remains constant (assuming no air resistance).

• Option A is incorrect because the total mechanical energy is not the difference between potential and kinetic energy; it is the sum.
• Option B is incorrect because there is no such difference between potential energy and gravitational energy.
• Option C is incorrect because friction energy doesn't directly apply in this context.

Thus, the correct answer is Option D: None of these.

• Option A (Blowing air into a balloon) involves pushing air into the balloon, not pulling.
• Option B (Cycling) involves applying force to the pedals, typically in a pushing motion, not pulling.
• Option C (Stretching a rubber band) involves pulling the rubber band to stretch it.

Therefore, the correct answer is Option C: Stretching a rubber band.

In a nuclear power plant, the cooling tower is the part that helps to dissipate excess heat and prevent thermal pollution of nearby lakes or rivers. It cools the water that has been used in the plant to absorb heat from the reactor. This cooled water is then returned to the environment at a safer temperature.

• Option A (Reactor) generates heat through nuclear fission but does not control thermal pollution.
• Option B (Coolant/moderator) helps control the temperature and reactions within the reactor but is not responsible for preventing thermal pollution.
• Option D (Control rod) helps control the rate of the nuclear reaction, but it doesn't deal with thermal pollution.

Thus, the correct answer is Option C: Cooling tower.

The capacity to do work is called energy. Energy is required to perform any work, and it can exist in different forms, such as kinetic energy, potential energy, thermal energy, etc.

• Option A (Force) is an influence that can cause an object to move or change its motion, but it is not the capacity to do work.
• Option C (Machine) is a device used to perform work, but it is not the capacity to do work.
• Option D (Movement) refers to motion, which results from the application of energy but is not the capacity itself.

Thus, the correct answer is Option B: Energy.