Question 1 :
Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it. How much work is done by the men in lifting the box? $(g=10 ms^{-2})$
Question 2 :
The work done on an object does not depend upon the
Question 3 :
A light and a heavy object have the same momentum. Find out the ratio of their kinetic energies. Which one has a larger kinetic energy?
Question 4 :
The kinetic energy of an object of mass m moving with a velocity of 5 $\frac{m}{s}$ is 25 J. What will be its kinetic energy when its velocity is doubled?
Question 5 :
A 150 kg car engine develops 500 W for each kg. What force does it exert in moving the car at a speed of $20 ms^{–1}?$
Question 7 :
An automobile engine propels a 1000 kg car (A) along a levelled road at a speed of $36 kmh^{–1}$.Now, suppose after travelling a distance of 200 m, this car collides with another stationary car (B) of same mass and comes to rest. Let its engine also stop at the same time. Now car (B) starts moving on the same level road without getting its engine started. Find the speed of the car (B) just after the collision.
Question 8 :
Is it possible that an object is in the state of accelerated motion due to external force acting on it, but no work is being done by the force.
Question 9 :
A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
Question 10 :
An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?
Question 11 :
The kinetic energy of a body moving with a certain velocity is ________ to the work done on it to make it acquire that velocity.
Question 12 :
1 J is the amount of work done on an object when a force of 1 N displaces it by ____ along the line of action of the force.
Question 13 :
A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
Question 15 :
The Jog Falls in Karnataka state are nearly 20 m high. 2000 tonnes of water falls from it in a minute. Calculate the equivalent power if all this energy can be utilized? $(g = 10 ms^{–2})$
Question 16 :
A girl having mass of 35 kg sits on a trolley of mass 5 kg. The trolley is given an initial velocity of $4 ms^{–1}$ by applying a force. The trolley comes to rest after traversing a distance of 16 m. How much work is done by the girl?
Question 17 :
A donkey is carrying a load on its back. Is it a work?
Question 18 :
An object having capability to do work is said to possess energy. Energy has the same unit as that of work.
Question 19 :
Write an expression for the work done when a force is acting on an object in the direction of its displacement.
Question 21 :
A car is accelerated on a levelled road and attains a velocity 4 times of its initial velocity. In this process the potential energy of the car
Question 22 :
The kinetic energy of an object of mass, m moving with a velocity of 5 m $s^{-1}$ is 25 J. What will be its kinetic energy when its velocity is doubled? What will be its kinetic energy when its velocity is increased three times?
Question 23 :
Find the energy possessed by an object of mass 10 kg when it is at a height of 6 m above the ground. Given, g = 9.8 m $s^{-2}$.
Question 24 :
Find the energy in kW h consumed in 10 hours by four devices of power 500 W each.
Question 25 :
If an agent does a work W in time t, then power is given by: _________.
Question 26 :
Can any object have momentum even if its mechanical energy is zero?
Question 27 :
Energy exists in nature in several forms such as kinetic energy, potential energy, heat energy, chemical energy etc. The sum of the kinetic and potential energies of an object is called its mechanical energy.
Question 28 :
A mass of 10 kg is at a point A on a table. It is moved to a point B. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force?
Question 29 :
Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it. How much work do they do in just holding it? $(g=10 ms^{-2})$
Question 31 : <img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d2f2f59b460d7261f662.PNG' />
The above image shows, A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force shown in figure. Let us take it that the force acts on the object through the displacement. What is the work done in this case?
Question 32 :
The unit of energy and work
called joule, is named after James Prescott Joule.
Question 33 : <img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d2e1f59b460d7261f64a.png' />
Look at the above image. In each of the following a force, F is acting on an object of mass, m. The direction of displacement is from west to east shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative, positive or zero resctively.
Question 34 :
Certain force acting on a 20 kg mass changes its velocity from 5 m$s^{-1}$ to 2 m$s^{-1}$. Calculate the work done by the force.
Question 35 :
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy?
Question 36 :
A certain household has consumed 250 units of energy during a month. How much energy is this in joules?
Question 37 :
The gravitational potential energy of an object at a point above the ground is defined as the work done in raising it from the ground to that point against gravity.
Question 38 :
An object of mass m is moving with a constant velocity v. How much work should be done on the object in order to bring the object to rest?
Question 40 :
In case of negative work the angle between the force and displacement is
Question 41 :
A girl pulls a trolley and the trolley moves through a distance. The girl has exerted a force on the trolley and it is displaced. Therefore, work is done.
Question 42 :
A battery lights a bulb. Describe the energy changes involved in the process.
Question 43 :
Does the transfer of energy take place when you push a huge rock with all your might and fail to move it? Where is the energy you spend going?
Question 44 :
Find the energy in kWh consumed in 10 hours by four devices of power 500 W each.
Question 45 :
An object of mass 12 kg is at a certain height above the ground. If the potential energy of the object is 480 J, find the height at which the object is with respect to the ground. Given, g = 10 m $s^{-2}$.
Question 46 :
Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it. Why do they get tired whie holding it?
Question 47 :
A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not?
Question 48 :
Soni says that the acceleration in an object could be zero even when several forces are acting on it. State true or false.
Question 50 :
A body is falling from a height h. After it has fallen a height $\frac{h}{2}$ , it will possess
