Physics-

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### Question

#### An object of mass is tied to a string of length and a variable horizontal force is applied on it which starts at zero and gradually increases until the string makes an angel with the vertical. Work done by the force is

#### The correct answer is:

#### or

(Since, change in kinetic energy is zero)

Here, work done by tension = 0

work done by fore of gravity

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### Related Questions to study

physics-

#### A block of mass kg sliding on a smooth horizontal surface with a velocity meets the spring of spring constant fixed at one end as shown in figure. The maximum compression of the spring and velocity of block as is returns to the original position respectively are

When block strikes the spring, the kinetic energy of block converts into potential energy of spring ie,

Or

When block returns to the original position, again potential energy converts into kinetic energy of the blocks, so velocity of the block is same as before but its sign changes as it goes to mean position.

Or

When block returns to the original position, again potential energy converts into kinetic energy of the blocks, so velocity of the block is same as before but its sign changes as it goes to mean position.

#### A block of mass kg sliding on a smooth horizontal surface with a velocity meets the spring of spring constant fixed at one end as shown in figure. The maximum compression of the spring and velocity of block as is returns to the original position respectively are

physics-General

When block strikes the spring, the kinetic energy of block converts into potential energy of spring ie,

Or

When block returns to the original position, again potential energy converts into kinetic energy of the blocks, so velocity of the block is same as before but its sign changes as it goes to mean position.

Or

When block returns to the original position, again potential energy converts into kinetic energy of the blocks, so velocity of the block is same as before but its sign changes as it goes to mean position.

physics-

#### The relationship between the force F and position of a body is as shown in figure. The work done in displacing the body from to m will be

Work done=area enclosed by graph

=area of ABNM + area of CDEN - area of EFGH + area of HIJ

=

=area of ABNM + area of CDEN - area of EFGH + area of HIJ

=

#### The relationship between the force F and position of a body is as shown in figure. The work done in displacing the body from to m will be

physics-General

Work done=area enclosed by graph

=area of ABNM + area of CDEN - area of EFGH + area of HIJ

=

=area of ABNM + area of CDEN - area of EFGH + area of HIJ

=

physics-

#### Three objects and are kept in a straight line on a frictionless horizontal surface. These have masses and respectively. The object moves towards with a speed and makes an elastic collision with it. Thereafter, makes completely inelastic collision with . All motions occur on the same straight line. Find the final speed (in ) of the object

After elastic collision strikes to with velocity of . Now collision between and is perfectly inelastic

By the law of conservation of momentum

#### Three objects and are kept in a straight line on a frictionless horizontal surface. These have masses and respectively. The object moves towards with a speed and makes an elastic collision with it. Thereafter, makes completely inelastic collision with . All motions occur on the same straight line. Find the final speed (in ) of the object

physics-General

After elastic collision strikes to with velocity of . Now collision between and is perfectly inelastic

By the law of conservation of momentum

physics-

#### The relation between the displacement of an object produced by the application of the variable force is represented by a graph shown in the figure. If the object undergoes a displacement from to the work done will be approximately equal to

Work done = Area under curve and displacement axis

= Area of trapezium

As the area actually is not trapezium so work done will be more than approximately

= Area of trapezium

As the area actually is not trapezium so work done will be more than approximately

#### The relation between the displacement of an object produced by the application of the variable force is represented by a graph shown in the figure. If the object undergoes a displacement from to the work done will be approximately equal to

physics-General

Work done = Area under curve and displacement axis

= Area of trapezium

As the area actually is not trapezium so work done will be more than approximately

= Area of trapezium

As the area actually is not trapezium so work done will be more than approximately

physics-

#### In the given curved road, if particle is released from then

If the surface is smooth then the kinetic energy at never be zero

If the surface is rough, the kinetic energy at be zero. Because, work done by force of friction is negative. If work done by friction is equal to then, net work done on body will be zero. Hence, net change in kinetic energy is zero. Hence, (b) is correct If the surface is rough, the kinetic energy at must be lesser than . If surface is smooth, the kinetic energy at is equal to The reason is same as in (a) and (b)

If the surface is rough, the kinetic energy at be zero. Because, work done by force of friction is negative. If work done by friction is equal to then, net work done on body will be zero. Hence, net change in kinetic energy is zero. Hence, (b) is correct If the surface is rough, the kinetic energy at must be lesser than . If surface is smooth, the kinetic energy at is equal to The reason is same as in (a) and (b)

#### In the given curved road, if particle is released from then

physics-General

If the surface is smooth then the kinetic energy at never be zero

If the surface is rough, the kinetic energy at be zero. Because, work done by force of friction is negative. If work done by friction is equal to then, net work done on body will be zero. Hence, net change in kinetic energy is zero. Hence, (b) is correct If the surface is rough, the kinetic energy at must be lesser than . If surface is smooth, the kinetic energy at is equal to The reason is same as in (a) and (b)

If the surface is rough, the kinetic energy at be zero. Because, work done by force of friction is negative. If work done by friction is equal to then, net work done on body will be zero. Hence, net change in kinetic energy is zero. Hence, (b) is correct If the surface is rough, the kinetic energy at must be lesser than . If surface is smooth, the kinetic energy at is equal to The reason is same as in (a) and (b)

physics-

#### A body of mass slides down a curved track which is quadrant of a circle of radius . All the surfaces are frictionless. If the body starts from rest, its speed at the bottom of the track is

By conservation of energy,

#### A body of mass slides down a curved track which is quadrant of a circle of radius . All the surfaces are frictionless. If the body starts from rest, its speed at the bottom of the track is

physics-General

By conservation of energy,

physics-

#### A 10 kg brick moves along an -axis. Its acceleration as a function of its position is shown in figure. What is the net work performed on the brick by the force causing the acceleration as the brick moves from to m?

According to the graph the acceleration varies linearly with the coordinate . We may write , where is the slope of the graph.

From the graph

The force on the brick is in the positive -direction and according to Newton’s second law, its magnitude is given by

If is the final coordinate, the work done by the force is

From the graph

The force on the brick is in the positive -direction and according to Newton’s second law, its magnitude is given by

If is the final coordinate, the work done by the force is