Question 1 :
An object having capability to do work is said to possess energy. Energy has the same unit as that of work.
Question 3 :
The work done by a force can be either positive or negative.
Question 4 :
Write an expression for the work done when a force is acting on an object in the direction of its displacement.
Question 5 :
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 6 :
A green plant is carrying out photosynthesis. Is it a work?
Question 7 :
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 8 :
A lamp consumes 1000 J of electrical energy in 10 s. What is its power?
Question 9 :
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 10 :
What are the various energy transformations that occur when you are riding a bicycle?
Question 13 :
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 14 : <img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d2e1f59b460d7261f64b.png' />
In the above fig. A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force. Let us take it that the force acts on the object through the displacement. What is the work done in this case?
Question 15 :
In case of negative work the angle between the force and displacement is
Question 16 :
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 17 :
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 18 :
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy?
Question 19 :
When a body falls freely towards the earth, then its total energy
Question 20 :
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 21 :
The kinetic energy possessed by an object of mass, m and moving with a uniform velocity, v is _______.
Question 22 :
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 23 :
According to the law of conservation of energy, energy can only be transformed from one form to another; it can neither be created nor destroyed. The total energy before and after the transformation always remains constant.
Question 24 :
If an agent does a work W in time t, then power is given by: _________.
Question 25 : <img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d2e2f59b460d7261f64c.png' />
In the above fig. A force of 5 N is acting on an object. The object is displaced through 2 m in the direction of the force. If the force acts on the object all through the displacement, then what is the work done?
Question 26 :
Power is defined as the rate of doing work. The SI unit of power is watt. 1 W = 1 J/s.
Question 27 :
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 28 :
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 29 :
An electric heater is rated 1500 W. How much energy does it use in 10 hours?
Question 30 :
A donkey is carrying a load on its back. Is it a work?
Question 31 :
An electric heater is rated 1500 W. How much energy does it use in 10 hours?
Question 33 :
Can there be displacement of an object in the absence of any force acting on it?
Question 34 :
Compare the power at which a 250 g squirrel climbing up on a tree at a rate of $0.5 ms^{–1}$ is moving upwards against the force of gravity. $(given g = 10 ms^{–2})$
Question 35 :
The relation connecting the initial velocity $\left(u\right)$ and final velocity $\left(v\right)$ of an object moving with a uniform acceleration a, and the displacement, s is__________.
Question 36 :
The energy possessed by a body due to its change in position or shape is called the potential energy.
Question 37 :
Work done on an object by a force would be zero if the displacement of the object is zero.
Question 38 :
Avinash can run with a speed of $8 ms^{-1}$ against the frictional force of 10 N, and Kapil can move with a speed of $3 ms^{–1}$ against the frictional force of 25 N. Who is more powerful and why?
Question 39 :
Can any object have momentum even if its mechanical energy is zero?
Question 40 :
The work done on an object does not depend upon the
Question 41 :
The energy used in one hour at the rate of 1kW is called 1 kW h. TRUE OR FALSE?
Question 43 :
Find the energy in kWh consumed in 10 hours by four devices of power 500 W each.
Question 44 :
What is the work done by the force of gravity on a satellite moving round the earth?
Question 45 :
What is the work to be done to increase the velocity of a car from 30 km $h^{-1}$ to 60 km $h^{-1}$ if the mass of the car is 1500 kg?
Question 46 :
A pair of bullocks exerts a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in ploughing the length of the field?
Question 47 :
If an electric iron of 1200 W is used for 30 minutes everyday, find electric energy consumed in the month of April.
Question 48 :
A boy of mass 50 kg runs up a staircase of 45 steps in 9 s. If the height of each step is 15 cm, find his power. Take g = 10 m $s^{-2}$.
Question 49 :
A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy?
Question 50 :
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?
