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

11th Standard

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Physics

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

20 x 1 = 20
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. 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)

$\sqrt{gR}$

4. 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 %

5. 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

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. 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%

8. In case of negative work, the angle between the force and displacement is

(a)

00

(b)

900

(c)

450

(d)

1800

9. A force$\overrightarrow { F } =3\hat { i } +c\hat { j } +2\hat { k }$ acting on a particle causes a displacement $\overrightarrow { S } =(2\hat { i } -3\hat { j } +4\hat { k } )$ in its own direction. If the work done is 8J, then the value of c is

(a)

0

(b)

6

(c)

2

(d)

1

10. Water stored in a dam possesses

(a)

no energy

(b)

electrical energy

(c)

kinetic energy

(d)

potential energy

11. An iron sphere of mass 8 kg has the same diameter as a copper sphere of mass 4 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same

(a)

acceleration

(b)

momenta

(c)

Potential Energy

(d)

Kinetic Energy

12. How are joule (J) and ergs related

(a)

1 J = 107 erg

(b)

1 erg = 10-7 J

(c)

1 J = 10-7 erg

(d)

none

13. A bullet is fired and gets embedded in a block kept on table. If table is frictionless, then

(a)

Kinetic Energy gets conserved

(b)

Potential Energy gets conserved

(c)

Momentum conserved

(d)

both (a) and (c)

14. A particle of mass m1 is moving with a velocity v, and another of mass mis moving with velocity v2 Both of them have the some momentum but their kinetic energies are E1 and E2 respectively. If =m1 > m2 the

(a)

E1<E2

(b)

$\frac{E_1}{E_2}=\frac{m_1}{m_2}$

(c)

E1>E2

(d)

E1=E2

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

(a)

upon the system by a non-conservative force

(b)

upon the system by a conservative force

(c)

By a system against conservative force

(d)

By a system against non conservative force

16. In an elastic collision

(a)

both momentum and kinetic energy are conserved

(b)

only kinetic energy is conserved

(c)

both momentum and kinetic energy are not conserved

(d)

only momentum is conserved

17. 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)

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

18. Which one of the following is not a conservative force?

(a)

Gravitational force

(b)

Electrostatic force between two changes

(c)

Magnetic force, between two magnetic dipoles

(d)

Frictional force

19. The total work done on a particle is equal to the change in its kinetic energy:

(a)

always

(b)

only if the force acting on the body are conservative

(c)

only in the internal frame

(d)

only if no external force is acting

20. An object is thrown vertically upwards as it rises its total energy:

(a)

decreases

(b)

increases

(c)

remains constant

(d)

none of the above