#### 11th Standard Physics Work, Energy and Power English Medium Free Online Test One Mark Questions 2020 - 2021

11th Standard

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Physics

Time : 00:20:00 Hrs
Total Marks : 20

20 x 1 = 20
1. A uniform force of (2$\hat { i }$+$\hat { j }$) N acts on a particle of mass 1 kg. The particle displaces from position (3$\hat { j }$+$\hat { k }$) m to (5$\hat { i }$+3$\hat { j }$) m. The work done by the force on the particle is

(a)

9 J

(b)

6 J

(c)

10 J

(d)

12 J

2. A body of mass 1 kg is thrown upwards with a velocity 20 ms-1 It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction?(Take g = 10 ms-2)

(a)

20 J

(b)

30 J

(c)

40 J

(d)

10 J

3. The coefficient of restitution e for a perfectly elastic collision is

(a)

1

(b)

0

(c)

$\alpha$

(d)

-1

4. The work done by the conservative force for a closed path is

(a)

always negative

(b)

zero

(c)

always positive

(d)

not defined

5. If the potential energy of the particle is $\alpha -\frac { \beta }{ 2 } { x }^{ 2 }$ then force experienced by the particle is

(a)

F=$\frac { \beta }{ 2 } { x }^{ 2 }$

(b)

F=βx

(c)

F=-βx

(d)

F=-$\frac { \beta }{ 2 } { x }^{ 2 }$

6. A spring of force constant k is cut into two pieces such that one piece is double the length of the other. Then, the long piece will have a force constant of

(a)

$\frac{2}{3}$k

(b)

$\frac{3}{2}$k

(c)

3k

(d)

6k

7. A cricket ball falls from a height of 40 m. What is the velocity with which the ball hits the ground?

(a)

40 m/s

(b)

20 m/s

(c)

16 m/s

(d)

28 m/s

8. A particles moves along x-axis from x = 0 to x = 7m under the influence of a force given by f(x)=12-2x+3x2 then the workdone is,

(a)

205 J

(b)

390 J

(c)

378 J

(d)

291 J

9. A ball bounces to 75% of its original height. Calculate the mechanical energy lost in each bounce.

(a)

0.40

(b)

0.35

(c)

0.25

(d)

0.20

10. Which one of the following is not the unit of energy?

(a)

joule

(b)

Nm

(c)

kW

(d)

kWh

11. When a body falls freely towards the earth, then its T.E.

(a)

increases

(b)

decreases

(c)

remains constant

(d)

first increases and then decreases

12. A boy is carrying a school bag of 5 kg mass on his back and moves 100 m on a levelled road. The work done against the gravitational force is (g = 10 ms-1)

(a)

5J

(b)

500J

(c)

0.5J

(d)

zero

13. A simple pendulum hanging freely and at rest vertical because in that position

(a)

Kinetic Energy is zero

(b)

Kinetic Energy is minimum

(c)

Potential Energy is zero

(d)

Potential Energy is minimum

14. A ball whose Kinetic Energy is E is projected at an angle of 45° to the horizontal. The kinetic energy of the ball at the highest point of its flight will be

(a)

E

(b)

$\frac{E}{\sqrt2}$

(c)

$\frac{E}{2}$

(d)

zero

15. A gun of mass M fires a bullet of mass m with maximum speed v. G.T. m < M. The kinetic energy of the gun will be

(a)

$\frac{1}{2}$mv2

(b)

$\frac{1}{2}$Mv2

(c)

more than $\frac{1}{2}$mv2

(d)

less than$\frac{1}{2}$mv2

16. Two bodies of masses m and 4m are moving with equal kinetic energies. The ratio of their linear momenta is

(a)

1 : 2

(b)

1 : 4

(c)

4: 1

(d)

1: 1

17. A shell, in flight explodes into four unequal parts. Which is conserved?

(a)

potential energy

(b)

momentum

(c)

kinetic energy

(d)

both a and c

18. Power can be expressed as

(a)

$\overrightarrow { F } .\overrightarrow { v }$

(b)

$\frac { 1 }{ 2 } \overrightarrow { F } .{ v }^{ 2 }$

(c)

$\overrightarrow { F } .{ t }$

(d)

$\overrightarrow { F } \times\overrightarrow { v }$

19. A particle is acted upon by a force of constant magnitude which is always perpendicular to the velocity of the particle, the motion of the particles takes place in a plane. It follows that:

(a)

its kinetic energy is constant

(b)

its acceleration is constant

(c)

its velocity is constant

(d)

it moves in a straight line.

20. Two equal masses m1 and m2 moving along the same straight line with velocities + 3 m/s and -5 m/s respectively collide elastically. Their velocities after the collision will be respectively

(a)

- 4 m/s and +4 m/s

(b)

+4 m/s for both

(c)

- 3 m/s and +5 m/s

(d)

- 5 m/s and + 3 m/s