**Work Done by a Variable Force MCQ and Answers** are must for the aspirants who are preparing for various competitive examination. It covers the concept of Work, Energy and Power which is very important for any competitive exams. This Law of Work, Energy and Power topic is given most importance in various competitive exams like JEE Main, JEE Advanced, NEET, AIIMS etc.

## Work Done By A Variable Force MCQ

**1. A bucket filled with water weighing 20 kg is raised from a well of depth 20 m. If the linear density of the rope is 0.2 kg/m, the work done is _____ (Assume g = 10m/s2)**

a) 4000 J

b) 4040 J

c) 4400 J

d) 4800 J

**Answer: **c

**2. A force F = (5i – 3j +2k) N moves a particle from r1 = (2i + 7j + 4k) m to r2 = (5i + 2j + 8k) m. What is the work done by the force?**

a) 18 J

b) 28 J

c) 38 J

d) 48 J

**Answer: **c

**3. A person of mass 50 kg carrying a load of 20 kg walks up a staircase. The width and height of each step are 0.25 m and 0.2 m respectively. What is the work done by the man in walking 20 steps?(Assume g = 10m/s**^{2})

^{2})

a) 800 J

b) 1600 J

c) 2000 J

d) 2800 J

**Answer: **d

**4. A chain of length 4 m is kept on a table. 2 m of the chain hangs freely from the table’s edge. The mass of the whole chain is 8 kg. What is the work done to pull the whole chain onto the table? (Assume g = 10m/s2)**

a) 20 J

b) 40 J

c) 60 J

d) 80 J

**Answer: **b

**5. The area under the force (F) versus displacement (x) graph gives work.**

a) True

b) False

**Answer: **a

**6. An object of mass 1kg is subjected to a variable force in x-direction. The force function is F = x**^{2} N. What is the work done in moving the object from x = 2 to 5?

^{2}N. What is the work done in moving the object from x = 2 to 5?

a) 40

b) 39

c) 38

d) 69

**Answer: **b

**7. What is the SI unit of variable force?**

a) Newtons

b) Joules

c) Ampere

d) Mole

**Answer: **a

**8. A spring is stretched by a length x, then the potential energy stored in it changes by 0.5*k*x**^{2}, where k is the spring constant.

^{2}, where k is the spring constant.

a) True

b) False

**Answer: **a

**9. A force of 600 N elongates a spring from its natural length of 18 cm to a length of 20 cm. What is the work done?**

a) 116J

b) 114J

c) 118J

d) 120J

**Answer: **b

**10. Which of the following is not a variable force?**

a) F = x

b) F = y^{2}

c) F = 2

d) F = 2*t

**Answer: **c

**11. Which of the following is not a conservative force?**

a) Gravitational force

b) Spring force

c) Friction force

d) Magnetic force

**Answer: **c

**12. A force F = x + 1 N acts on a particle in x direction. What is the work done from x = 2m to 5 m?**

a) 10.5 J

b) 14.5 J

c) 13.5 J

d) 0.5 J

**Answer: **c

**13. What is the value of spring constant if force of 200 N is acting on it and the spring is compressed by 2m?**

a) 100 kgs-^{2}

b) 100 kgs-^{1}

c) 100 kg^{2}s^{2}

d) 100 Kgs

**Answer: **a

**14. The length of a smooth inclined plane of 30-degree inclination is 5 m. The work done in moving a 10 kg mass from the bottom of the inclined plane to the top is _____ Joules. (Assume g = 10m/s2)**

a) 250

b) 1000

c) 1250

d) 500

**Answer: **a

**15. A rope has a uniform mass density of 0.4 kg/m. The rope is 10 m long and is lowered into a 10 m deep pit. The bottom part of the rope just touches the bottom of the pit. What is the work done to pull the rope out of the well completely? (Assume g = 10m/s2)**

a) 200 J

b) 400 J

c) 2000 J

d) 4000 J

**Answer: **a