A 10 N force moving a body 2 m in its direction does 20 J of work, and the work done by the centripetal force in uniform circular motion is zero, so this Class 11 sheet opens with one calculation and one counter-intuitive zero. The answers record watt and 100 J.
Key Takeaways
10 N over 2 m in the force's direction gives 20 J of work (Q1).
The centripetal force does zero work in uniform circular motion (Q2).
Q4 records watt.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.A force of 10 N displaces a body by 2 m in the direction of the force. The work done is:
(a) 10 J(b) 20 J(c) 5 J(d) 12 J
2.The work done by the centripetal force on a body moving in uniform circular motion is:
(a) zero(b) positive(c) negative(d) equal to the kinetic energy
3.The kinetic energy of a body of mass 2 kg moving at 3 m/s is:
(a) 6 J(b) 18 J(c) 9 J(d) 4.5 J
4.The SI unit of power is the:
(a) watt(b) joule(c) newton(d) pascal
5.If the speed of a moving body is doubled, its kinetic energy becomes:
(a) the same(b) double(c) half(d) four times
6.The work done in raising a body of mass 5 kg to a height of 2 m is (g = 10 m/s²):
(a) 10 J(b) 50 J(c) 20 J(d) 100 J
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.Define work and write its SI unit. State two situations in which the work done by a force is zero.
8.State the work-energy theorem.
9.Define potential energy and write the expression for the gravitational potential energy of a body of mass m at a height h near the earth's surface.
10.Define power and write its SI unit. Give the relation between power, force and velocity.
11.State the law of conservation of mechanical energy.
12.Define kinetic energy and derive its expression in terms of mass and velocity.
13.Define a conservative force and give one example.
14.Distinguish between elastic and inelastic collisions.
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A force of 50 N acts on a body and displaces it by 10 m along the direction of the force. Using W = F × s, find the work done.
16.A body of mass 5 kg is raised to a height of 4 m. Taking g = 10 m/s² and using W = mgh, find the work done and the gravitational potential energy gained by the body.
17.A body of mass 2 kg moves with a speed of 10 m/s. Using K = ½mv², find its kinetic energy and the work required to bring it to rest.
18.A pump lifts 1000 kg of water to a height of 20 m in 100 s. Taking g = 10 m/s² and using P = mgh/t, find the power delivered by the pump.
19.A body of mass 1 kg is dropped from a height of 20 m. Using conservation of energy, v = √(2gh), find its speed just before it reaches the ground. Take g = 10 m/s².
20.A car of mass 1000 kg accelerates from 5 m/s to 15 m/s. Using K = ½mv², find the increase in kinetic energy and the work done on the car.
Answer Key
1. b) 20 J
2. a) zero
3. c) 9 J
4. a) watt
5. d) four times
6. d) 100 J
7. Refer to solution guide.
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20. Refer to solution guide.
End of Worksheet
People Also Ask
How much work does a 10 N force doing 2 m of displacement in its direction do?
20 J, option (b) in this worksheet (Q1).
What is the work done by the centripetal force in uniform circular motion?
Zero, option (a) in this worksheet (Q2).
What is the SI unit of power?
The watt, option (a) in this worksheet (Q4).
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