# CBSE Class 11-Physics: Work Energy and Power Assignment 2

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**Question 1:**

The Potential Energy U in Joule of a particle of mass moving in the plane is given by the formula

Here x and y are coordinates of the particle in meter

The particle is at at and

**i** and **j** are the unit vectors across x and y axis respectively

a) Find the force acting on the particle

b) Find the kinetic energy of the particle at time t

c) Find the time at which it crosses x axis and y axis and Kinetic energy at that points

d) Find the coordinates of the particle as a function of time

e) Find the Potential Energy of the particle at time

**Question 2**

A body of mass m is displaced from Position A to B by the forces and Given

Position Vector of Point

Position Vector of Point

Find the total work done by the resultant forces

**Question 3**

A block of mass m is placed on an inclined plane of angle . The Friction Coefficient between the block and surface of the incline plane is . The block is placed at height H From the bottom of the incline plane. Find the velocity with which the block reaches the bottom of the incline

**Question 4**

A block moves horizontally on a rough floor. The Friction Coefficient between the

block and surface is . The block strikes the light spring of spring constant K with velocity

a) Find the maximum compression of the spring

b) Find the work done by the Friction force

c) Find the work done by the spring forces

**Question 5**

An object of mass is given an initial velocity on the rough horizontal surface in a positive axis direction. The Friction Coefficient between the object and surface is . At , and i is the unit vector across axis

a) Find the instantaneous Power P developed by the Friction forces

b) Find the velocity of the object at time t

c) Find the time taken by the object before coming to rest

d) Find the total work done by the frictional forces

e) Find the mean power developed by the frictional forces during the whole motion

f) if varies as per the following

Find the value of the when instantaneous power is maximum

**Question 6**

A car of mass M accelerates starting from rest along axis. The engine is supplying constant Power W. Initially car is at

a) Find the position of the car as a function of time

b) Find the velocity of car as a function of time

c) Find the acceleration of the car as a function of time

**Question 7**

A uniform chain of mass M and length L is lying on a friction less horizontal table with one fourth of its length hanging over of edge of the table. Find the amount of work done to pull the hanging part of the chain up the table

**Question 8**

A box is dragged across a floor by a rope which makes an angle of with the horizontal. The tension in the rope is while the box is dragged is .

a) Find the work done

b) What will be the work done if the rope is horizontal