Work Energy and Power Test

Result

Work Energy and Power Test - 70

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Weekly Quiz Competition

Question 1
1 / -0

A stone tied to the end of a string of 1 m long is whirled in a horizontal circle with a constant speed. If the stone makes 22 revolutions in 44 s, what is the magnitude & direction of acceleration of the stone:

A
$$\pi^2 \ m/s^2$$ and direction along the tangent to the circle.

B
$$\pi^2 \ m/s^2$$ and direction along the radius towards the centre.

C
$$\frac{\pi^2}{4} \ m/s^2$$ and direction along the radius towards the centre.

D
$$\pi^2 \ m/s^2$$ and direction along the radius away from the centre.

Solution
Question 2
1 / -0

One end of a light spring of force constant $$k$$ is fixed to the ceiling. The other end is fixed to a block of mass $$m$$. Initially the spring is relaxed. The work done by an external agent to lower the hanging body of mass $$m$$ slowly till it comes to equilibrium is:

A
$$3\ \dfrac{m^{2}g^{2}}{2\ k}$$

B
$$\dfrac{m^{2}g^{2}}{2\ k}$$

C
$$-3 \dfrac{m^{2}g^{2}}{2\ k}$$

D
$$-\dfrac{m^{2}g^{2}}{2\ k}$$

Solution
Question 3
1 / -0

A body of mass $$10\ kg$$ moves according to the relation $$x=t^{2}+2t^{3}$$. The work done by the force in the first $$2s$$ is.

A
$$7840\ J$$

B
$$1960\ J$$

C
$$3920\ J$$

D
$$4840\ J$$

Solution
Question 4
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A stone of mass 1 kg is tied to the end of a string of $$1m$$ length. It is whired in a vertical circel. If the velocity of the stone at the top be $$4m/s$$. What is the tension in the string (at that instant)?

A
$$6N$$

B
$$16N$$

C
$$5N$$

D
$$10N$$

Solution
Question 5
1 / -0

Work done from $$d=0\ m$$ to $$d=4\ m$$

A
$$12.5\ J$$

B
$$15\ J$$

C
$$17.5\ J$$

D
$$20\ J$$

Solution
Question 6
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A block of mass $$10kg$$ is moving in x-direction with a constant speed of $$10m/sec$$. It is subjected to a force $$F=-0.1x $$ Joules/meter during its travel from $$x=20$$ meters to $$x=30$$ meters. Its final kinetic energy will be-

A
$$475$$ joules

B
$$450$$ joules

C
$$275$$ joules

D
$$250$$ joules

Solution
Question 7
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Mass $$2m$$ is kept on a smooth circular track of mass $$m$$ , which is kept on a smooth horizontal surface. The circular track is given a horizontal velocity $$\sqrt{2gR}$$ towards left and released. The maximum height reached by $$2m$$ will be ?

A
$$\dfrac {R}{4}$$

B
$$\dfrac {R}{2}$$

C
$$\dfrac {R}{3}$$

D
$$\dfrac {2R}{3}$$

Solution
Question 8
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A smooth ball $$A$$ collides elastically with an another identical ball $$B$$ with velocity $$10 m/s$$ at an angle of $$30^o$$ from the line joining their centres $$C_1$$ and $$C_2$$ , then mark INCORRECT statement :

A
Velocity of ball $$A$$ after collision is $$15 m/s$$

B
Velocity of ball $$B$$ after collision is $$5.4 m/s$$

C
Both the balls move at right angles an collision

D
KE will not be conserved here, because collision is not head on
Question 9
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A stone is tied to a rope is rotated in a vertical circle with unifrom speed. if the difference between maximum and minimum tension in the rope is $$20N$$, mass of the stone in $$Kg$$ is $$(g=10m/s^{2})$$

A
$$0.75$$

B
$$1.0$$

C
$$1.5$$

D
$$0.5$$

Solution
Question 10
1 / -0

If initial charge on all the capacitors were zero, work done by the battery in the circuit shown is

A
$$0.2 mJ$$

B
$$200 mJ$$

C
$$0.4 mJ$$

D
$$400 mJ$$

Solution