Work Energy and Power Test

Result

Work Energy and Power Test - 72

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Weekly Quiz Competition

Question 1
1 / -0

A gun is mounted on a trolley free to move on horizontal tracks. Mass of gun and trolley $$25$$ kg. Gun fires a two shells of mass $$5$$ kg each other. Velocity of shells with roll to gun is $$60 $$ m/s . In above question, velocity of gun with respect to ground after firing second shell is-

A
$$12$$ m/s

B
$$18$$ m/s

C
$$50$$ m/s

D
$$60$$ m/s

Solution
Question 2
1 / -0

Two spring of spring constant k and 3k are stretched separately by same force. The ratio of the potential energy stored in them respectively will be

A
3 : 1

B
9 : 1

C
1 : 3

D
1 : 9

Solution
Question 3
1 / -0

The P.E of a certain spring a, when stretched from natural through a distance $$0.3m$$, is $$10J$$. The amount of work in joule that must be done on this spring to stretch it through an additional distance $$0.15m$$ will be

A
$$10J$$

B
$$20J$$

C
$$7.5J$$

D
$$12.5J$$

Solution
Question 4
1 / -0

A vertical spring of force constant $$100 N/m$$ is attached with a hanging mass of $$10 $$ kg. Now an external force is applied on the mass so that the spring is stretched by the additional $$2$$ m, The work done by the force F is ( $$g= 10 m/s^2$$)

A
$$200 $$ J

B
$$400 $$ J

C
$$450 $$ J

D
$$600 $$ J

Solution
Question 5
1 / -0

A ball of mass $$10kg$$ moving with velocity $$20m/s$$ collides elastically with wall and rebound with the same speed.Then the magnitude of change in momentum of the ball will be

A
Zero

B
$$300kg$$ $$m/s$$

C
$$400kg$$ $$m/s$$

D
$$100kg$$ $$m/s$$

Solution
Question 6
1 / -0

$$540$$ calories of heat convert $$1\ cubic\ centimeter$$ of water at $$100^{o}\ C$$ into $$1671\ cubic\ centimeter$$ of steam at $$100^{o}\ C$$ at a pressure of one atmosphere. Then the work done against the atmospheric pressure is nearly:

A
$$540\ cal$$

B
$$40\ cal$$

C
$$zero\ cal$$

D
$$500\ cal$$

Solution
Question 7
1 / -0

A bucket full of water weighs $$5$$ kg, it is pulled from a well $$20m$$ deep. There is a small hole In the bucket through which water leaks at a constant rate of $$0.2 k g m ^ { - 1 }.$$ The total work done in pulling the bucket up from the well is $$(g = 10 m s ^ { - 2 } )$$

A
$$600J$$

B
$$400J$$

C
$$100J$$

D
$$500J$$

Solution
Question 8
1 / -0

$$AB$$ is a long frictionless horizontal surface. One end of an ideal spring of spring constant $$K$$ is attached to a block of mass $$m$$ which is being moved left with constant velocity $$v _ { 1 }$$ and another end is free. Another block of mass $$2\mathrm { m }$$ is given a velocity $$3\mathrm { v }$$ towards the spring. The magnitude of work done by the external agent in moving $$m$$ with constant velocity $$v$$ in a long time is $$\beta$$ times $$m v ^ { 2 }$$. Find the value of $$\beta .$$

A
$$-5\ mv^2$$

B
$$-8\ mv^2$$

C
$$-3\ mv^2$$

D
None of these

Solution
Question 9
1 / -0

The average kinetic energy of an idea gas per molecule at $$25^{o}C$$, will be

A
$$6.1\times10^{-20}J$$

B
$$6.1\times10^{-21}J$$

C
$$6.1\times10^{-22}J$$

D
$$6.1\times10^{-23}J$$

Solution
Question 10
1 / -0

The mass of object X is $$M_1$$ and that of object Y is $$M_2$$. Keeping their kinetic energy constant, if the velocity of object Y is doubled the velocity of object X, what will be the relation between their masses?

A
$$M_1=2M_2$$

B
$$4M_1=M_2$$

C
$$M_1=4M_2$$

D
$$2M_1=M_2$$

Solution

Mass of object X = $$M_1$$ , Velocity of object X = $$v_1$$
Mass of object Y = $$M_2$$, Velocity of object Y = $$v_2$$
Also, $$v_2$$ = 2$$v_1$$
K.E is constant.

K.E$$_1$$ = K.E$$_2$$
$$\dfrac{1}{2}$$ $$M_1$$ $$v_1^2$$ = $$\dfrac{1}{2}$$ $$M_2$$ $$v_2^2$$
$$\dfrac{1}{2}$$ $$M_1$$ $$v_1^2$$ = $$\dfrac{1}{2}$$ $$M_2$$ $$(2v_1)^2$$

$$\dfrac{1}{2}$$ $$M_1$$ $$v_1^2$$ = $$\dfrac{1}{2}$$ $$M_2$$ $$4\ v_1^2$$

$$M_1$$ = 4 $$M_2$$