Question:
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.
Work and Energy
Q 1.
A body is thrown vertically upwards. Its velocity goes on decreasing. Write the change in kinetic energy when its velocity becomes zero.
Q 2.
A 60 kg person climbs stairs of total height 20 m in 2 min.Calculate the power delivered.
Q 3.
What do the machines need for their working ?
Q 4.
How does the wind move the blades of a wind-mill ?
Q 5.
Define potential energy.Derive an expression for the potential energy of a body of mass m,at a height h above the surface of the Earth.
Q 6.
Flowing water can rotate a turbine.What type of energy is used up by the turbine ?
Q 7.
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 8.
Name a machine that transforms muscular energy into useful mechanical work.
Q 9.
An object of mass 15 kg is moving with a uniform velocity of 4 m/s.What is the kinetic energy possessed by the object ?
Q 10.
What is the form of energy possessed by a running car?
Q 11.
A boy of mass 55 kg runs up a flight of 40 stairs,each measuring 0.15 m.Calculate the work done by the boy
Q 12.
Name two forms of mechanical energy.
Q 13.
A force of 7 N acts on an object.The displacement is,say 8 m,in the direction of the force,[in Fig.].Let us take it that the force acts on the object throughout the displacement What is the work done in this case ?
Q 14.
A freely falling object eventually stops on reaching the ground.What happens to its kinetic energy ?
Q 15.
Why do some engines require fuels like petrol and diesel ?
Q 16.
Can there be displacement of an object in the absence of any force acting on it ? Think.Discuss this question with your friends and teacher.
Q 17.
Is a person doing any work by holding a suitcase ?
Q 18.
A coolie carries a load of 50 kg on his head and walks on a level road upto 100 m.What is the work done by him ?
Q 19.
The velocity of a body moving in a straight line is increased by applying a constant force F,for some distance in the direction of the motion. Prove that the increase in the kinetic energy of the body is equal to the work done by the force on the body.
Q 20.
What is the work done by a constant force ?When is it positive,negative or zero ?
Q 21.
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?
Q 22.
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 23.
Fill in the blanks :
Ability to do work is called _______.
Q 24.
Name the device which converts electrical energy into mechanical energy.
Q 25.
Can a body have energy without having momentum ?
Q 26.
Name the type of energy possessed by a raised hammer?
Q 27.
How much work is done on a body of mass 1kg whirling on a circular path of radius 5m?
Q 28.
The work done by the heart is I J per beat.Calculate the power of the heart if it beats 72 times/min.
Q 29.
Write an expression for kinetic energy of an object
Q 30.
When is work done by a force zero ?
Q 31.
A body of mass 15 kg undergoes downward displacement of 40m under the effect of gravitational force. How much work is done? (take g = 10 m/s
2)
Q 32.
What is the kinetic energy of an object ?
Q 33.
What are the various energy transformations that occur when you are riding a bicycle ?
Q 34.
Is energy a vector quantity ?
Q 35.
Fill in the blanks :
A form of energy an object has because of its motion is called ________.
Q 36.
Define average power.
Q 37.
What do you mean by work ?Give its scientific conception.
Q 38.
What do you understand by the term energy ? Give its scientific conception.
Q 39.
What do you mean by the term potential energy ? Give some examples of bodies possessing potential energy ?
Q 40.
Name a few forms of energy and their transformation into each other.
Q 41.
What do you mean by power of an agent ? Give an expression for power.
Q 43.
Fill in the blanks :
Work done against a force is stored as _____.
Q 44.
Can a body have energy without possessing momentum?
Q 45.
Fill in the blanks :
Work done is defined as the product of _____ and ______ in the direction of force.
Q 46.
Fill in the blanks :
1 Joule = ____ × ____.
Q 47.
A battery lights a bulb. Describe the energy changes involved in the process.
Q 48.
What is a conservative forces? Give an example.
Q 49.
Mathematically show that law of conservation of energy holds true for a free falling object. Consider negligible air resistance.
Q 50.
A certain household has consumed 250 units of energy during a month. How much energy is this in joules?
