Question:
What are the various energy transformations that occur when you are riding a bicycle?
Answer:
The muscular energy of the cyclist transforms into kinetic (mechanical) energy. Due to movement of muscles, cyclist also produces heat. Thus muscular energy is converted into heat energy. The tyres of the cycle are in contact with road and experience friction. Due to friction, tyres get heated. Thus kinetic energy of tyres get converted to heat energy.
Muscular energy of cyclist ➟ Kinetic Energy + Heat energy
Kinetic Energy of Tires + Energy of Friction ➟ Heat Energy in tyres
Work and Energy
Q 1.
Fill in the blanks :
Work is a ______ (scalar/vector) quantity.
Q 2.
A force of 10 N moves a body with a constant speed of 2 m/s. Calculate the power of the body.
Q 3.
Fill in the blanks :
Work done on an object is _____ if displacement is zero.
Q 4.
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 5.
Fill in the blanks :
Work done by gravity on a falling body is available as ______ (kinetic/potential) energy on reaching the ground.
Q 6.
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 7.
A man exerts a force of 200 N in pulling a cart at a constant speed of 16 m/s.Calculate the power spent by the man.
Q 8.
Fill in the blanks :
Work done is defined as the product of _____ and ______ in the direction of force.
Q 9.
Fill in the blanks :
Work done is negative when the angle between force and displacement is ____ (acute/obtuse)
Q 10.
What do you understand by the term energy ? Give its scientific conception.
Q 11.
Write an expression for the kinetic energy of an object.
Q 12.
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 13.
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 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.
A battery lights a bulb.Describe the energy changes involved in the process
Q 16.
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 objjgft by the gravitational force ? Explain your answer.
Q 17.
Two bodies of masses m
1 and m
2 have equal kinetic energies. If p
1 and p
2 are their respective momentum, then ratio p
1 : p
2 is ___?
Q 18.
What are other forms of energies apart from mechanical energy? Does Law of Conservation of Energy apply to all of them?
Q 19.
A man does 200 J of work in 10 s and a boy does 100 J of work in 4 s.(a) Who is delivering more power ?
(b) Find the ratio of the power delivered by the man to that delivered by the boy.
Q 20.
How do you differentiate between energy and power ?
Q 21.
Is it possible to havfc a situation where mechanical energy (E) - potential energy (
) Is negative,i.e.,(E-
)< 0.
Q 22.
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 23.
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 24.
A certain household has consumed 250 units of energy during a month. How much energy is this in joules?
Q 25.
What are the units of work and energy ?
Q 26.
What is mechanical energy? What are its types?
Q 27.
What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.
Q 28.
Define 1 J of work.
Q 29.
What are the various energy transformations that occur when you are riding a bicycle ?
Q 30.
What is meant by the term potential energy ? Give its two examples.
Q 31.
Define kinetic energy.Give some examples of bodies possessing kinetic energy.
Q 32.
Fill in the blanks :
Work done against a force is stored as _____.
Q 33.
Does the work done on a load depend on the time taken to raise the load?
Q 34.
Can there be displacement of an object in the absence of any force acting on it?
Q 35.
A bullet of mass 0.03 kg moving with a speed of 400 m/s penetrates 12 cm into fixed block of wood.Calculate the average force exerted by the wood on the bullet.
Q 36.
Two bodies of equal masses move with uniform velocities v and 3 v respectively.Find the ratio of their kinetic energies.
Q 37.
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 increased three times ?
Q 38.
Name the type of energy possessed by a raised hammer.
Q 39.
What is the difference between potential energy and kinetic energy ?
Q 40.
What do you mean by work ?Give its scientific conception.
Q 41.
What do you mean by the law of conservation of energy ?
Q 42.
What do you mean by kinetic energy ? Derive an expression for the kinetic energy of an object of mass m moving with velocity,v.
Q 43.
Many people debate about whether there is a God,or what God is.Is God an individual personality,sitting up in heaven listening to and granting our requests,or is God simply all the energy that exists in the Universe,or is God simply nature or the laws of nature ?
Q 44.
Fill in the blanks :
Ability of a body to do work due to its position or configuration is known as _________ of the body.
Q 45.
Mathematically show that law of conservation of energy holds true for a free falling object. Consider negligible air resistance.
Q 46.
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 47.
What is the kinetic energy of an object ?
Q 48.
Write an expression for kinetic energy of an object
Q 49.
whether or not work is done in the light of your understanding of the term ‘work’.
(a) Suma is swimming in a pond.
(b) A donkey is carrying a load on its back.
(c) A wind-mill is lifting water from a well.
(d) A green plant is carrying out photosynthesis.
(e) An engine is pulling a train.
(f) Food grains are getting dried in the Sun.
(g) A sailboat is moving due to wind energy.
Q 50.
A certain household has consumed 250 units of energy during a month.How much energy is this in joules ?
