Question

4. In case of vertically projected body : [ ]

a) Potential energy decreases b) Potential energy increases

c) Kinetic energy decreases d) both b and c

5. A person holding a 5 kg of suitcase and waiting for the bus. The work done will be: [ ]

a) 59 J b) 5 J c) 0 J d) 0. 5 J

6. A body is displaced by 20 m, when a force of 20 N acts on the body. The work done is: [ ]

a) 20 J b) 200 J c) 400 J d) 40 J

7. A body of 10 kg is falling from the height of 50 m under the influence of gravitational force. Then

the work done is (g = 10 ms–2) : [ ]

a) 500 J b) 50 J c) 5000 J d) 5 J

8. Work done by an applied force of 20 N on a body moving on a rough horizontal plane with a

uniform velocity of 20 ms–1 in one second is : [ ]

a) 40 J b) 0 J c) 400 J d) 20 J

9. A force of 10 N acts on a body of mass 1 kg at rest. The work done by the force through a

distance of 80 m is : [ ]

a) 80 J b) 800 J c) 8 J d) 8000 J

10. As a body rolls down on an inclined plane, it has : [ ]

a) only kinetic energy b) only potential energy

c) both kinetic energy and potential energy d) neither kinetic energy nor potential energy​

Answer 1

Ur answer is d mate....

Answer 2

Answer:

The answers are as follows:

4.  d) both b and c

Explanation: This is because when a body is vertically projected,it is thrown against the gravity. Thus, the potential energy stored inside the body increases gradually, reducing the kinetic energy simultaneously.

5. c) 0J

Explanation: Since there is no displacement of force (here 5kg suitcase) from one place to another, no work is done by the person. Hence, the work done is zero.

6. c)400J

Explanation: $Work done= Force* Displacement (ie) WD=F*S$

Thus, here F=20N and S=20m

Therefore, W.D = 20*20 = 400J

Thus the work done by the body is 400J.

7. c) 5000J

Explanation: $Work done= Force* Displacement (ie) WD=F*S$;$Force= mg$

Here, m= 10kg; g=10$m/s^{2}$ and s= 50m

Therefore,

F= 10*10=100N

W.D = F*S=100*50=5000J

Thus the work done by the body is 5000J.

8. c)400J

Explanation: $Work done= Force* Displacement (ie) WD=F*S$

$Distance=Speed*time$

Here, F=20N; Speed=20m/s; time=1s

Thus, Distance=20*1=20m

Therefore, W.D = 20*20=400J

The work done by an applied force on a moving body on a rough horizontal plane is 400J.

9) b) 800J

Explanation: $Work done= Force* Displacement (ie) WD=F*S$

Here F=10N; and S=80m

Therefore W.D= 10*80=800J

Thus the work done by the body through a distance of 80m is 800J.

10) c) both kinetic energy and potential energy

Explanation: When a body rolls down, both the kinetic energy and potential energy acts on the body. According to law of conservation of energy, the potential energy gets converted into kinetic energy. Thus both energies come into act.

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