Work, Energy and Power MCQs

 

WORK,ENERGY AND POWER

Q1. A force of 6 N acts on a body of mass 3 kg producing a displacement of 10 m. The work done by the force is

a.      18 J

b.      30 J

c.       60 J

d.      36 J

       Q2. A body acted upon by a force of 25 N acquires acceleration of

2.5 ms-2 and covers a distance 10 m. If the body starts from rest then what is the kinetic energy acquired by it?

a.      25 J

b.      250 J

c.       75 J

d.      100 J

       Q3. A body at rest cannot have

a.      Potential energy

b.      Kinetic energy

c.       Electrical energy

d.      Both A and B

Q4. Which would have greater impact; a ball with mass m thrown with speed 20 m/s or a ball with mass m/2 thrown at speed 40 m/s?

a.      Ball with mass m

b.      Ball with mass m/2

c.       Both have the same kinetic energy

d.      Depends on the surface on which the balls are thrown

Q5. Calculate the distance between a man and a box when 100 J of work done to move the box with a force of 15 N.

       a.     16.6 m

       b.     26.6 m

c.       6 m

d.      6.6 m

Q6. A coolie was standing with two suitcases on his head and two bags in his hand. The luggage exerted a force of 159 N on him. What is the amount of work done by him?

      a.     159 J

      b.     79.5 J

                       c.       0 J
                           d.      318 J

Q7. Calculate the work done in moving a body of mass 50 kg through a height of 5 m. (g = 10m/s2)

a.     250 J

b.     2500 J

c.     25 x 103 J

d.    2.5 x 105J

Q8. A 500 kg cloth bag is pulled up a smooth plane 6 m long to a platform which is 4 m above the ground. The work done is (Take g = 10 ms-2)

a.      2 x 102 J

b.      2 x 103 J

c.       2 x 104 J

d.      2 x 105 J

Q9. 1 J is the energy required to do of work.

a.      1 N

b.      1 J

c.       9.8 N

d.      98 J

Q10. A crane lifts a block of mass 1000 kg through a vertical height of 15 m in 25 s. Calculate the power of crane. Given g = 10 m/s2.

a.     6000 W

b.      6 W

c.       600 W

d.      60 W

Q11. A body of mass 5 kg moving with an acceleration of 5 ms-2 gets a displacement of 2m, the work done by the force is

a.      25 J

b.      50 J

c.       75 J

d.      100 J

Q12. To lift 700 kg of water through a height of 10 m a pump is used. What will be the work done in operating the pump? (Take g = 10 m/s2)

a.     700 J

b.     70000 J

c.       7 x 106 J

d.      7 kJ

Q13. A diesel engine supplies 25,000 J of energy in 50 seconds.

What will be the power of the engine? a. 25000 W

b.     500 W

c.     7500 W

d.    250 W

Q14. A fish weighing 35 kg dives and hits the ground (zero height) with kinetic energy equal to 3500J. Find the height through which the fish dived. (Take g = 10 m/s2)

a.      100 m

b.      10 m

c.       20 m

d.      1 km

Q15. How much energy does a 150 W steam iron consume per second?

a.      15 W

b.      15 J

c.       150 J

d.    0.15 J

Q16. What happens to the K.E. of a body when 3/4th of its mass is removed and velocity is doubled?

a.     4K.E.     b)1/4K.E.              c)1/2K.E.       d)No change

Q17. If a force of 1 N is acting on an object that is moving through 10 m in a direction perpendicular to the force, then the work done is

a.      1 J

b.      10 J

c.       100 J

d.      Zero

Q18. A body of mass 44 kg is moving at a velocity of 10 m/s is brought to rest in 10 minutes, the work done is

a.      22 J

b.      220 J

c.     -2200J

d.    22000 J

 

Q19. How fast should a person of mass 50 kg run so that his kinetic energy is 625 J?

a.      5 Km/s

b.      5 m/s

c.       0.5 m/s

d.      15 km/s

Q20. A car of mass 50 kg starting from rest with a final velocity of 40 m/s travels for 20 seconds. What will be the acceleration and the work done to bring it to rest?

a.     1.5 m/s2 , 0.4 x 105 J

b.     2.0 m/s2 , 4.0 x 105 J

c.     2.0 m/s2 , 0.4 x 105 J

d.    1.5 m/s2 , 4.0 x 105 J

Q21. A stone weighing 1 kg is dropped from rest from a height of 4 m above the ground. When it has free-fallen 1 m its total energy with respect to the ground is

a.      20 J

b.      15 J

c.       30 J

d.      40 J

Q22. If a ball falls from a height h then the sum of its kinetic and potential energy after it falls through a distance is

a.      Equal to the potential energy at h

b.      Greater than the potential energy at h

c.       Lesser than its potential energy at h

       d.   Can be greater or lesser than its potential energy at h

                   Q23. Work done by a body is

a.      always negative

b.      always positive

c.       always zero

d.   negative, positive or zero

Q24. What is not true about energy?

a.      Energy can be stored.

b.      Energy can move from one object to another

c.       Energy can be transformed from one type of energy to another type of energy.

d.      Energy can be created.

Q25. A body of mass 4 kg has a momentum of 20 kg m/s, its K.E. is

a.      25 J

b.      50 J

c.       70 J

d.      100 J

Q26. If the velocity of a moving car is halved, its kinetic energy would

a.      Remain same

b.      Double

c.       Become Half

d.      Become one-fourth

Q27. A 1kW hair dryer is used for half an hour. How much energy is used?

a.      1 unit

b.      0.5 unit

c.       1.5 unit

d.      0.05 unit

Q28. The kinetic energy of a body changes from 12 J to 60 J due to the action of a force of 5 N on an object of mass 4 kg. The work done by the force is

a.      24 J

b.      36 J

c.       48 J

d.      60 J

      Q29. A lamp consumes 1000 J of energy in 10 s, what is its power?

a.     100 W

b.     1000 W

c.     100000W

d.    1kW

Q30. Two bodies of masses m and 4 m are moving with equal kinetic energy. The ratio of velocities with which they are traveling is

a.     1:2

b.     2:1

c.     3:4

d.    4:5

Q31. Water jet of an area of cross-section 2 cm2 strikes the wall normally with a velocity of 20 m/s and falls freely. The magnitude of force exerted on the wall is (Density of water = 1000 kg m-3)

a.      40 N

b.      60 N

c.       − 80 N

d.      100 N

Q32. Which one of the following is possessed by a freely falling body during its fall?

a.      Kinetic energy

b.      Potential energy

c.       Sound energy

d.      Both kinetic energy and potential energy

Q33. A girl weighing 45 kg jumps to a height of (1/2) m at the rate 10 times per minute. The power at which she is spending the energy is

a.      25 W

b.      50 W

c.       75 W

d.      100 W

Q34. When a ball is thrown vertically upwards its velocity keeps on decreasing. What happens to its kinetic energy when it reaches the maximum height?

a.      Kinetic energy is maximum at maximum height

b.      Kinetic energy is half the initial value

c.       Kinetic energy is zero

d.      Kinetic energy is double

Q35. The winners of long jump each weighing 56 kg, 40 kg and 45 kg stand on the podium. What is the work done by them on the podium while they receive the medals?

a.      141 J

b.      0 J

c.       282 J

d.      250 J

        Q36. Which of the following is not an example of potential energy?

a.      A moving car

b.      Water stored in the reservoir of dam

c.       A compressed spring

d.      A stretched rubber band

Q37. In which one of the following cases is work scientifically said to be done?

a.      Mira studies for her exam

b.      Manish pulls the trolley up to a certain distance

c.       Manoj pushes the wall with no change in the position of wall

d.      Mitiksha standing at a bus stop holding a bag in her hand.

Q38. Find the amount of work done in lifting a body of 5 kg through 10 m. Take g = 10 m/s2.

a.      5 J

b.      15 J

c.       50 J

d.      500 J

Q39. How much energy is consumed by a 40 W bulb in one minute?

a.     1.5 J

b.     0.66 J

c.     240 J

d.    2400 J

Q40. A boy climbs onto a wall that is 3.4 m high and gains 2250 J of potential energy. What is the mass of the boy? Take g = 9.8 m/s2

a.      50 kg

b.      67.5 kg

c.       62.5 kg

d.      70 kg

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