Question:
Fill in the blanks :
Work done on an object is _____ if displacement is zero.
Work and Energy
Q 1.
How do you differentiate between energy and power ?
Q 2.
The mass of a ball A is double the mass of another ball B.The ball A moves at half the speed of the ball B.Calculate the ratio of the kinetic energy of A to the kinetic energy of B.
Q 4.
Fill in the blanks :
Work done is positive when the angle between force and displacement is ____ (acute/obtuse)
Q 5.
A body of mass 120 g is taken vertically upwards to reach the height of 5m. Calculate work done. (Take g = 10 m/s
2)
Q 6.
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 ?
Q 7.
When an arrow is shot from a bow,it has kinetic energy.From where does it get the kinetic energy ?
Q 8.
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?
Q 9.
Can a body have energy without possessing momentum?
Q 10.
Fill in the blanks :
1 Joule = ____ × ____.
Q 11.
Write an expression for the kinetic energy of an object.
Q 12.
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why?
Q 13.
Give an example where potential energy is acquired by a body due to change of its shape.
Q 14.
Fill in the blanks :
Work done on an object is _____ if displacement is zero.
Q 15.
Fill in the blanks :
Work done is negative when the angle between force and displacement is ____ (acute/obtuse)
Q 16.
Fill in the blanks :
A force acting on a body shows a displacement in the direction normal to the direction of the force. It is said _______ done on the body.
Q 17.
Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
- Suma is swimming in a pond.
- A donkey is carrying a load on its back.
- A wind-mill is lifting water from a well.
- A green plant is carrying out photosynthesis.
- An engine is pulling a train.
- Food grains are getting dried in the sun.
- A sailboat is moving due to wind energy.
Q 18.
Identify the kind of energy possessed by a running athlete.
Q 19.
A freely falling object eventually stops on reaching the ground.What happens to its kinetic energy ?
Q 20.
Fill in the blanks :
Work done against a force is stored as _____.
Q 21.
A spring is stretched, will the work done by the stretching force positive or negative or zero.
Q 22.
Is work a scalar or vector quantity?
Q 23.
Can kinetic energy of an object be negative?
Q 24.
What is mechanical energy? What are its types?
Q 25.
Calculate potential energyof a person having 60 kg mass on the summit of Mt. Everest. Height of Mt. Everest is 8848 m from sea level. (g = 9.8 m/s
2)
Q 26.
What is Kilowatt hour?
Q 27.
A bullet of mass 20 g is found to pass two points 30 m apart in 4 s ? Assuming the -speed to be constant,find its kinetic energy.
Q 28.
What is the kinetic energy of an object?
Q 29.
Fill in the blanks :
Work done against gravity in lifting a mass is stored as ______. Numerically, it is equal to m ×_ ×__.
Q 30.
Fill in the blanks :
The sum of P.E. and K.E. is called __________.
Q 31.
A heavy stone is lowered to the ground with the help of rope. Is the work done by the applied force positive or negative?
Q 32.
What is a conservative forces? Give an example.
Q 33.
If the momentum of a body is increased
n times, its kinetic energy increases (a) n times (b) 2n times (c) √n times (d) n
2 times
Q 34.
Is work a scalar quantity or a vector quantity ?
Q 35.
What are the units of work and energy ?
Q 36.
The global climate has always fluctuated.Millions of years ago,some parts of the world that are now quite warm, were covered with ice,and over recent centuries,average temperatures have risen and fallen in cycles.What is new,however,is that current and future climate change will be caused not just by natural events but also by activities of human beings.Suggest three simple ways to help save the climate of our planet.
Q 37.
Define 1 J of work.
Q 38.
Is Work a scalar or vector quantity?
Q 39.
Certain force acting on a 20 kg mass changes its velocity from 5 m/s to 2 m/s. Calculate the work done by the force.
Q 40.
State the relation between commercial unit of energy and joules.
Q 41.
Name a few forms of energy and their transformation into each other.
Q 42.
Fill in the blanks :
Ability of a body to do work due to its position or configuration is known as _________ of the body.
Q 43.
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?
Q 44.
Fill in the blanks :
Work done by gravity on a falling body is available as ______ (kinetic/potential) energy on reaching the ground.
Q 45.
Fill in the blanks :
Kinetic Energy = ½ × _ × _
Q 46.
Fill in the blanks :
If the mass is doubled while its speed remains the same, the kinetic energy will be _____ (be same/double/four times) of the initial kinetic energy.
Q 47.
Assuming the earth revolves around the sun in a perfect circular orbit due to centripetal force exerted by the Sun. Is the work done by the Sun positive or negative.
Q 48.
What is the relationship between kinetic energy and work?
Q 49.
A person throws a stone of mass 3kg. It crosses the top of a wall of 2m high at a speed of 4m/s. What is the total mechanical energy possessed by the stone when it crosses the wall?(Take g = 10 m/s)
Q 50.
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
