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#### Nature of Physical World and Measurement-1marks

11th Standard

Reg.No. :
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Physics

Time : 00:30:00 Hrs
Total Marks : 20
Part-A
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 ball of mass 1 kg and another of mass 2kg are dropped from a tall building whose height is 80 m. After, a fall of 40 m each towards Earth, their respective kinetic energies will be in the ratio of

(a)

$\sqrt2:1$

(b)

$1:\sqrt2$

(c)

2:1

(d)

1:2

3. 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

4. A body of mass 4 m is lying in xy-plane at rest. It suddenly explodes into three pieces. Two pieces each of mass m move perpendicular to each other with equal speed v. The total kinetic energy generated due to explosion is

(a)

mv2

(b)

$\frac{3}{2}$mv2

(c)

2mv2

(d)

4mv2

5. The potential energy of a system increases, if work is done

(a)

by the system against a conservative force

(b)

by the system against a non-conservative force

(c)

upon the system by a conservative force

(d)

upon the system by a non- conservative force

6. What is the minimum velocity with which a body of mass m must enter a vertical loop of radius R so that it can complete the loop?

(a)

$\sqrt{2gR}$

(b)

$\sqrt{3gR}$

(c)

$\sqrt{5gR}$

(d)

$\sqrt{gR}$

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

(a)

always negative

(b)

zero

(c)

always positive

(d)

not defined

8. If the linear momentum of the object is increased by 0.1% then the kinetic energy is Increased by

(a)

0.1 %

(b)

0.2 %

(c)

0.4 %

(d)

0.01 %

9. 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=-$\frac { \beta }{ 2 } { x }^{ 2 }$

10. A wind-powered generator converts wind U(x) energy into electric energy. Assume that the generator converts a fixed fraction of the wind energy intercepted by its blades into electrical energy. For wind speed v, the electrical power output will be proportional to,

(a)

v

(b)

v2

(c)

v3

(d)

v4

11. A particle is placed at the origin and a force F = kx is acting on it (where k is a positive constant). If U (0) = 0, the graph of U(x) versus x will be (where U, is the potential , energy function)

(a)

(b)

(c)

(d)

12. A particle which is constrained to move along x-axis, is subjected to a force in the same direction which varies with the distance x of the particle from the origin as F(x) =kx + ax3. Here, k and a are positive constants. For x≥0, the functional form of the potential, energy U(x) of the particles

(a)

(b)

(c)

(d)

13. 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

14. Convert 1 kWh in joule

(a)

1.2 ｘ102 J

(b)

2.4 ｘ104 J

(c)

3.6 ｘ106 J

(d)

4.4 ｘ103 J

15. A motor which is capable of raising 2,000 litres of water in 3 mins from a well 120 m deep. So what is the power of a motor?

(a)

8.730 kW

(b)

7.840 kW

(c)

11.652kW

(d)

13.066kW

16. If momentum of a body increases by 100% then what will be percentage increase in its kinetic energy?

(a)

200%

(b)

100%

(c)

300%

(d)

400%

17. 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

18. A particles along y axis from y = 1 m to y = 3 m under the influence of a force given by f(y)=6-2y+3y2 then the work done is,

(a)

48 J

(b)

50 J

(c)

-48 J

(d)

- 50 J

19. An engine pumps water continuously through a hose. Water leaves the hose with a velocity v and m is the mass per unit length of the water of the jet. What is the rate at which kinetic energy is imparted to water?

(a)

${{1}\over{2}}{m}{v}^{2}$

(b)

mv3

(c)

${{1}\over{2}}{m}{v}^{3}$

(d)

${{1}\over{2}}{m}{v}^{2}$

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