Question 1 :
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 2 :
What are the various energy transformations that occur when you are riding a bicycle?
Question 3 :
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 5 :
A wind-mill is lifting water from a well. Is it a work?
Question 6 :
A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back? $(g = 10 m s^{–2})$
Question 7 :
The weight of a person on a planet A is about half that on the earth. He can jump upto 0.4 m height on the surface of the earth. How high he can jump on the planet A?
Question 8 :
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 9 :
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy?
Question 10 :
An object in motion possesses what is known as the kinetic energy of the object.
Question 11 :
What are the two conditions that are really essential for a work to be done?
Question 12 :
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 13 :
A certain household has consumed 250 units of energy during a month. How much energy is this in joules?
Question 14 :
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 15 :
State true or false : There can be displacement of an object in the absence of any force acting on it.
Question 16 :
If an electric iron of 1200 W is used for 30 minutes everyday, find electric energy consumed in the month of April.
Question 17 :
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 18 :
Does any work take place when you push a huge rock with all your might and fail to move it?
Question 19 :
Work done on an object by a force would be zero if the displacement of the object is zero.
Question 20 :
If an agent does a work W in time t, then power is given by: _________.
Question 21 : <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 22 :
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 23 :
An automobile engine propels a 1000 kg car along a levelled road at a speed of $36 kmh^{–1}$. Find the power if the opposing frictional force is 100 N.
Question 24 :
The work done by a force can be either positive or negative.
Question 25 :
Kamali is preparing for examinations. She spends lot of time in studies. She reads lots of books. In common parlance, she is ‘working hard’. But is it really a work?
Question 26 :
Two girls, each of weight 400 N climb up a rope through a height of 8 m. We name one of the girls A and the other B. Girl A takes 20 s while B takes 50 s to accomplish this task. What is the power expended by each girl?
Question 28 :
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 29 :
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 30 :
The energy possessed by a body due to its change in position or shape is called the potential energy.
Question 31 :
An object having capability to do work is said to possess energy. Energy has the same unit as that of work.
Question 32 :
An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.
Question 33 :
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 34 :
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 36 :
Certain force acting on a 20 kg mass changes its velocity from 5 $\frac{m}{s}$to 2 $\frac{m}{s}$. Calculate the work done by the force.
Question 37 :
A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy?
Question 38 :
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 on the trolley?
Question 39 :
Can there be displacement of an object in the absence of any force acting on it?
Question 40 :
Work done on an object is defined as the magnitude of the force multiplied by the distance moved by the object in the direction of the applied force. The unit of work is joule:$ 1 joule = 1 newton \times 1 metre.$ Is the statement true or false?
Question 41 :
The energy used in one hour at the rate of 1kW is called 1 kW h. TRUE OR FALSE?
Question 42 :
What is the work done by the force of gravity on a satellite moving round the earth?
Question 43 :
What is the formula of potential energy of an object ?
Question 44 :
A donkey is carrying a load on its back. Is it a work?
Question 45 :
Can any object have momentum even if its mechanical energy is zero?
Question 46 :
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 47 :
Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her?
Question 48 :
Can any object have mechanical energy even if its momentum is zero?
Question 49 :
Find the energy in kW h consumed in 10 hours by four devices of power 500 W each.
Question 50 :
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.
