Work, Energy and Power One Mark Question

11th Standard

Reg.No. :
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Physics

Time : 00:30:00 Hrs
Total Marks : 10
10 x 1 = 10
1. 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

2. A particle of mass m is being rotated on a vertical circle of radius r. If the speed of particle at the highest point be v, then

(a)

mg=$\frac{mv^{2}}{r}$

(b)

mg>$\frac{mv^{2}}{r}$

(c)

mg<$\frac{mv^{2}}{r}$

(d)

mg≥$\frac{mv^{2}}{r}$

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

(a)

1

(b)

0

(c)

$\alpha$

(d)

-1

4. 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

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

(a)

always negative

(b)

zero

(c)

always positive

(d)

not defined

6. Two equal masses m1 and m2 are moving along the same straight line with velocities 5ms-1 and -9 ms-1 respectively. If the collision is elastic, then calculate the velocities after the collision of m1 and mrespectively

(a)

-4ms-1 and 10 ms-1

(b)

10ms-1 and 0 ms-1

(c)

-9ms-1 and 5 ms-1

(d)

5ms-1 and 1 ms-1

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. 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

9. 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)

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

10. 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