Home | Work, Energy and Power: Multiple choice questions with answers

Multiple choice questions with Answers, Solution and Explanation

1.
A uniform force of (2iˆ+ ˆj) N acts on a particle of mass 1 kg. The particle displaces
from position (3 ˆj + ˆk ) m to (5iˆ+3ˆj)
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 2 kg 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)
√2 : 1

(b)
1 : √2

(c)
2 : 1

**(d) 1 : 2**

3.
A body of mass 1 kg is thrown upwards with a velocity 20 m s^{−1}. It
momentarily comes to rest after attaining a height of 18 m. How much energy is
lost due to air friction?. (Take g= 10ms^{-2} )

**(a) 20 J **

(b)
30 J

(c)
40 J

(d)
10 J

4.
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) ½ mv ^{2}_{ }**

b)
mv^{2}_{ }

c)
½ mu^{2}_{ }

d)
mu^{2}_{ }

5.
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)
mv^{2}

**(b) 3/2 mv ^{2}**

(c)
2mv^{2}

(d)
4mv^{2}

6.
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

7.
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)
√(2gR)

(b)
√(3gR)

**(c) √(5gR) **

(d)
√(gR)

8.
The work done by the conservative force for a closed path is

(a)
always negative

**(b) zero**

(c)
always positive

(d)
not defined

9.
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%

10.
If the potential energy of the particle is α - β/2 x^{2}, then force
experienced by the particle is

(a)
F=β/2 x^{2}

(b)
F=βx

**(c) F=-βx **

(d)
F=-β/2 x^{2}

11.
A wind-powered generator converts wind 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)
v^{2}

**(c) v ^{3} **

(d)
v^{4}

12.
Two equal masses m_{1} and m_{2} are moving along the same
straight line with velocities 5ms^{-1} and -9ms^{-1}
respectively. If the collision is elastic, then calculate the velocities after
the collision of m_{1} and m_{2}, respectively

(a)
-4ms^{-1} and 10 ms^{-1}

(b)
10ms^{-1} and 0 ms^{-1}

**(c) -9ms ^{-1} and 5 ms^{-1}**

(d)
5 ms^{-1} and 1 ms^{-1}

13.
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)

**Ans: c**

14.
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+ax^{3}.

Here,
*k* and a are positive constants. For x
≥ 0, the functional form of the potential energy U(x) of the particle is

**Ans: d**

15.
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)
2/3 k

**(b) 3/2 k**

(c)
3k

(d)
6k

Answers

1)
c 2) d 3) a 4) a 5) b

6)
a 7) c 8) b 9) b 10) c

11)
c 12) c 13) c 14) d 15) b

Tags : Physics , 11th Physics : Work, Energy and Power

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