Question:
What is a horsepower?
Answer:
A horsepower (hp) is another unit of power. 1 hp = 746 Watts
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.
Name a machine that transforms muscular energy into useful mechanical work.
Q 3.
How do you differentiate between energy and power ?
Q 4.
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 5.
What do you mean by work ?Give its scientific conception.
Q 6.
Define kinetic energy.Give some examples of bodies possessing kinetic energy.
Q 7.
Is work a scalar or vector quantity?
Q 8.
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 9.
What is the relationship between kinetic energy and work?
Q 10.
From where the falling raindrops gains kinetic energy?
Q 11.
State the relation between commercial unit of energy and joules.
Q 12.
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 13.
What do the machines need for their working ?
Q 14.
What is the difference between potential energy and kinetic energy ?
Q 15.
Fill in the blanks :
Work done against a force is stored as _____.
Q 16.
Two friends Ram and Shyam, each having weight of 40 kg, go for rock climbing. Ram climbs to a height of 3 m in 10 s. and Shyam covers the same height in 12 s. Is the work done by Ram and Shyam equal ? or not ? Compare the power of Ram and Shyam.
Q 17.
Is it possible that a force acts on a body still the work done is zero? Explain with an example.
Q 18.
Can a body have energy without possessing momentum?
Q 19.
Fill in the blanks :
A force acting on a body shows a displacement in the direction of the force. It is said _______ is done on the body.
Q 20.
Fill in the blanks :
Work done is defined as the product of _____ and ______ in the direction of force.
Q 21.
Fill in the blanks :
Work done on an object is _____ if displacement is zero.
Q 22.
Fill in the blanks :
Work done is positive when the angle between force and displacement is ____ (acute/obtuse)
Q 23.
Fill in the blanks :
Work done is negative when the angle between force and displacement is ____ (acute/obtuse)
Q 24.
Fill in the blanks :
An object moving in a circular orbit. The work done by the centrepetal force acting on the object is ______ (zero/non-zero).
Q 25.
A pendulum of length 1m and with a bob of mass 1 kg swings in a vertical plane. Find the work done (from the below said choices) by weight of the bob when it moves from position A to B (as shown in figure). (Take g = 10 m/sec^2)
a. 4J
b. -4J
c. -5 J
d. 5 J
Q 26.
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 27.
An object of mass m is raised from the the earth to an height of equal to the radius of the earth (R). Calculate the gain in potential energy by the object. Assume gravity of the earth is g.
Q 28.
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 29.
What is the kinetic energy of an object?
Q 30.
Write an expression for the kinetic energy of an object.
Q 31.
Fill in the blanks :
Work done against gravity in lifting a mass is stored as ______. Numerically, it is equal to m ×_ ×__.
Q 32.
Fill in the blanks :
Work done by gravity on a falling body is available as ______ (kinetic/potential) energy on reaching the ground.
Q 33.
Fill in the blanks :
Kinetic Energy = ½ × _ × _
Q 34.
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 35.
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 36.
Does the work done on a load depend on the time taken to raise the load?
Q 37.
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?
Q 38.
A spring is stretched, will the work done by the stretching force positive or negative or zero.
Q 39.
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 40.
Write an expression for the kinetic energy of an object in terms (i) velocity (
v) of an object (ii) in terms of momentum (
p) of an object.
Q 41.
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 42.
Can kinetic energy of an object be negative?
Q 43.
What is mechanical energy? What are its types?
Q 44.
The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why?
Q 45.
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 46.
What are the various energy transformations that occur when you are riding a bicycle?
Q 47.
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 48.
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 49.
Name the type of energy possessed by a raised hammer?
Q 50.
Identify the kind of energy possessed by a running athlete.
