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CBSE Class 9 Work and Energy — practice questions

Explore 63 free Work and Energy questions in CBSE Class 9 Science. Open each question or exercise to read its content, reference answers and available explanation.

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Work and Energy questions and exercises with answers

Showing questions 1–30 of 63.

The SI unit of work is the:Read the answer and worked solution →When a goalkeeper stops a football, the force she applies on the ball does:Read the answer and worked solution →A girl applies a force of 50 N to push a box and the box moves 4 m in the direction of the force. How much work is done?Read the answer and worked solution →A man pushes a wall with a force of 200 N. The wall does not move. How much work has the man done?Read the answer and worked solution →The work-energy theorem states that the work done on an object by all forces equals:Read the answer and worked solution →Calculate the kinetic energy of a 2 kg object moving at 10 m/s.Read the answer and worked solution →A 5 kg bag is lifted slowly from the ground to a height of 2 m. Taking g = 10 m/s², the work done against gravity is:Read the answer and worked solution →If the velocity of an object doubles, its kinetic energy:Read the answer and worked solution →A child slides down a smooth slide from rest, starting at a height of 5 m. Ignoring friction and taking g = 10 m/s², the velocity at the bottom is approximately:Read the answer and worked solution →As per your syllabus, what is the SI unit of WORK?Read the answer and worked solution →As per your syllabus, 1 joule equals which combination of SI base units?Read the answer and worked solution →As per your syllabus, Science, ENERGY is defined as which property?Read the answer and worked solution →As per your syllabus, what is the SI unit of ENERGY — the same as that of work?Read the answer and worked solution →As per your syllabus, what is the WORK-ENERGY THEOREM?Read the answer and worked solution →As per your syllabus, what is KINETIC ENERGY?Read the answer and worked solution →As per your syllabus, what is the formula for the KINETIC ENERGY of an object of mass m moving at speed v?Read the answer and worked solution →As per your syllabus, if the MASS of an object doubles (while its speed stays the same), how does its KINETIC ENERGY change?Read the answer and worked solution →As per your syllabus, an object with mass 2 kg moving at 10 m/s has what KINETIC ENERGY?Read the answer and worked solution →As per your syllabus, what is the PE of a 200 g cricket ball at a height of 10 m (taking g = 10 m/s²)?Read the answer and worked solution →As per your syllabus, Science, POWER is defined as which quantity?Read the answer and worked solution →As per your syllabus, what is the SI unit of POWER?Read the answer and worked solution →As per your syllabus, after whom is the SI unit of POWER (watt) named?Read the answer and worked solution →As per your syllabus, 1 HORSEPOWER (hp) is approximately equal to how many watts?Read the answer and worked solution →As per your syllabus, a weightlifter lifts a 75 kg mass by 2 m in 5 seconds (taking g = 10 m/s²). What POWER does she require?Read the answer and worked solution →As per your syllabus, what is the mechanical advantage of a FIXED PULLEY?Read the answer and worked solution →As per your syllabus, a LEVER consists of three parts. Which is NOT one of them?Read the answer and worked solution →A 2 kg cricket ball moving at 30 m/s has a kinetic energy of:Read the answer and worked solution →A 5 kg bag lifted to a height of 3 m above the ground (g = 10 m/s²) has gravitational POTENTIAL ENERGY of:Read the answer and worked solution →The SI unit of POWER is the:Read the answer and worked solution →The COMMERCIAL UNIT of electrical energy, used on electricity bills, is the:Read the answer and worked solution →

Worked practice questions

The SI unit of work is the:

  1. Newton (N)
  2. Pascal (Pa)
  3. Watt (W)
  4. Joule (J)
Show answer and solution

Correct answer: D. Joule (J)

Work = Force × displacement, so its unit is N × m = joule (J). We have 1 J = 1 N × 1 m. So 1 J = 1 kg·m²·s⁻². Watt is the unit of power, newton of force, pascal of pressure.

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When a goalkeeper stops a football, the force she applies on the ball does:

  1. Positive work
  2. Infinite work
  3. Zero work
  4. Negative work
Show answer and solution

Correct answer: D. Negative work

The force she applies on the ball is opposite to the ball's direction of motion (it's trying to stop the ball). When force and displacement are in opposite directions, the work done is negative.

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A girl applies a force of 50 N to push a box and the box moves 4 m in the direction of the force. How much work is done?

  1. 100 J
  2. 12.5 J
  3. 54 J
  4. 200 J
Show answer and solution

Correct answer: D. 200 J

Work = Force × displacement = 50 N × 4 m = 200 J. The force and displacement are in the same direction, so the work is positive.

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