EASY
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A force F acting on an object varies with distance x as shown here. The force is in N and x in m. The work done by the force in moving the object from x=0 to x=6 m is

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Important Questions on Work, Energy and Power

EASY
A satellite revolves around a planet in a circular orbit. What is the work done by the satellite at any instant? Give a reason.
EASY

A lawn roller has been pushed through a distance of 80 m by applying a force of 50 kg.wt in a direction inclined at 60° with the ground. Calculate the work done on the roller.

MEDIUM
A force acts on a body and displaces it by a distance S in a direction at an angle θ with the direction of force. What should be the value of θ to get the maximum positive work?
HARD
A block of mass m, lying on a smooth horizontal surface, is attached to a spring (of negligible mass) of spring constant k. The other end of the spring is fixed, as shown in the figure. The block is initially at rest in its equilibrium position. If now the block is pulled with a constant force F, the maximum speed of the block is:
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EASY
Two springs of spring constants K and 2K are stretched by same force. If W1 and W2 are the energies stored in them respectively then
MEDIUM

Identify the correct statements from the following:

(A) Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket is negative

(B) Work done by gravitational force in lifting a bucket out of a well by a rope tied to the bucket is negative

(C) Work done by friction on a body sliding down an inclined plane is positive

(D) Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity is zero

(E) Work done by the air resistance on an oscillating pendulum is negative

Choose the correct answer from the options given below:

MEDIUM
A body of mass 8 kg, under the action of a force, is displaced according to the equation s=t24 m, where 't' is the time. Find the work done by the force in the first 4 seconds.
EASY
A particle moves from a point - 2i^+5j^ to 4j^+3k^ when a force of 4i^+3j^ N is applied. How much work has been done by the force?
EASY
A particle of mass 10 g is thrown vertically upwards with a speed of 20 m s-1. The work done by the gravitational force during the time the particle moves upward is
EASY

Assertion A : The work done by the electrostatic force is zero when a point charge moves in a circular path around another charge.

Reason R : The dot product of force and displacement vectors gives work done.

MEDIUM
A block of mass m is kept on a platform which starts from rest with a constant acceleration g2 upwards, as shown in the figure. Work done by normal reaction on block in time t is,

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EASY
The work done to raise a mass m from the surface of the earth to a height h, which is equal to the radius of the earth is:
MEDIUM
When a rubber-band is stretched by a distance x, it exerts a restoring force of magnitude
F = ax + bx2 where a and b are constants. The work done in stretching the unstretched rubber-band by L is :
EASY
A wire fixed at the upper end stretches by length l by applying a force F. The work done in stretching is 
MEDIUM
Two similar springs P and Q have spring constants KP and KQ, such that KP>KQ. They are stretched, first by the same amount (case a), then by the same force (case b). the work done by the springs WP and WQ are related as respectively, in case
MEDIUM

A block of mass m slides from rest at a height H on a frictionless inclined plane as shown in the figure. It travels a distance d across a rough horizontal surface with coefficient of kinetic friction μ and compresses a spring of spring constant k by a distance x  before coming to rest momentarily. Then the spring extends and the block travels back attaining a final height of h.

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Then 

MEDIUM
A time dependent force F=6t acts on a particle of mass 1 kg. If the particle starts from the rest, the work done by the force during the first 1 sec will be:
EASY
The work done by a given force on a body depends only on
HARD
A force F=-5i^-7j^+3k^ acting on a particle causes a displacement s=3i^+2j^+ak^ in its own direction. If the work done is 14 J, then the value of a is:
MEDIUM
Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m s-1. Take g constant with a value 10 m s-2. The work done by the (i) gravitational force and the (ii) resistive force of air is