Question:
Define kinetic energy.Give some examples of bodies possessing kinetic energy.
Answer:
Refer to Art. 5.5,Page 264.
Work and Energy
Q 1.
How do you differentiate between energy and power ?
Q 2.
A body is thrown vertically upwards. Its velocity goes on decreasing. Write the change in kinetic energy when its velocity becomes zero.
Q 3.
Name a machine that transforms muscular energy into useful mechanical work.
Q 4.
Define kinetic energy.Give some examples of bodies possessing kinetic energy.
Q 5.
What do you mean by work ?Give its scientific conception.
Q 6.
What do you mean by the term potential energy ? Give some examples of bodies possessing potential energy ?
Q 7.
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 8.
What are the various energy transformations that occur when you are riding a bicycle ?
Q 9.
Name the type of energy possessed by a raised hammer.
Q 10.
What do the machines need for their working ?
Q 11.
An electric bulb of 60 W is used for 6 h per day.Calculate the ‘units’ of energy consumed in one day by the bulb
Q 12.
Define 1 J of work.
Q 13.
Define average power.
Q 14.
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 15.
Flowing water can rotate a turbine.What type of energy is used up by the turbine ?
Q 16.
How does the wind move the blades of a wind-mill ?
Q 17.
What is the difference between potential energy and kinetic energy ?
Q 18.
What do you mean by the law of conservation of energy ?
Q 19.
Can a body have energy without having momentum ?
Q 20.
A force of 5 N is acting on an object.The object is displaced through 2 m in the direction of the force.[in Fig.].If the force acts all through the displacement,find the work done by the force.
Q 21.
Write an expression for kinetic energy of an object
Q 22.
Is it possible to havfc a situation where mechanical energy (E) - potential energy (
) Is negative,i.e.,(E-
)< 0.
Q 23.
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 24.
What type of energy is possessed by a cricket ball just before being caught by a fielder ?
Q 25.
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 =
.
Q 26.
Is work a scalar quantity or a vector quantity ?
Q 27.
An electric heater is rated 1500 W.How much energy does it use in 10 hours ?
Q 28.
When is work done by a force zero ?
Q 29.
What do you mean by power of an agent ? Give an expression for power.
Q 30.
A box is pulled across a floor by applying a force of 100N at an angle of 60 degrees above the horizontal. How much work is done by the applying force in pulling the object to a distance of 8m?
Q 31.
Fill in the blanks :
Work done against a force is stored as _____.
Q 32.
Fill in the blanks :
Work done is positive when the angle between force and displacement is ____ (acute/obtuse)
Q 33.
The kinetic energy of an object of mass, m moving with a velocity of 5 m/s 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?
Q 34.
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.
Q 35.
What is Kilowatt hour?
Q 36.
A porter lifts a luggage of 15 kg from the ground and puts it on his head 1.5 m above the ground.Calculate the work done by him on the luggage.
Q 37.
The recent horrific storm surge flooding New Jersey and New York in US by Hurricane Sandy was almost prefectly predicted well in advance,but was more extreme than the average person might expect from a minimal hurricane.There is a metric that quantifies the energy of a storm based on how far out tropical-storm force winds extend from the centre,known as Integrated Kinetic Energy (IKE).
(i) What is Sandy’s ranking in terms of IKE among all the hurricanes witnessed so far?
(ii) What is the IKE of Sandy?
(iii) How was Sandy different from Hurricane Katrina ?
(iv) Which human value did Sandy generate among the people round the globe?
Q 38.
Is Work a scalar or vector quantity?
Q 40.
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 41.
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 42.
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 43.
Calculate the power of an engine required to lift 105 kg of coal per hour from a mine 360 m deep.
Q 44.
What are the units of work and energy ?
Q 45.
How does an object possessing energy perform work ? What is the unit of energy ?
Q 46.
Fill in the blanks :
A stretched rubber band acquires _________(potential/kinetic) energy.
Q 47.
Is it possible that a force acts on a body still the work done is zero? Explain with an example.
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.
What is the form of energy possessed by a running car?
Q 50.
What do you mean by kinetic energy ? Derive an expression for the kinetic energy of an object of mass m moving with velocity,v.
