(maximum, power, energy, watt, 746, positive, joule , Kinetic, displacement 1N, force, 0.746 1m, mechanical energy, work)
a) Work is measured as a product of____ and_____.
b) One fuel work is said to be done when a force of___ displaces a body by___.
c) The SI unit of work is____.
d) If the force and displacement are parallel to each other, the work done is___ and___ .
e) Kilowatt-hour is the unit of____ .
f) The SI unit of power is___ .
g) Horsepower is the unit of ____ .
h) The energy of a body due to its motion is called___ energy.
i) 1 horsepower = ____W = _____ kW.
j) The CGS unit of energy is____ .
k) The sum potential and kinetic energy of a body is called its____ .
2) Complete the following statement by choosing the word/words from those given in the brackets:
a) In a circular path, the work done by a body is____ (zero/ not zero)
b) Power is a____(scalar/vector) quantity.
c) If the mass of a body is doubled, its kinetic energy gets ____(doubled/4 times)
d) The bob of a simple pendulum has maximum____(Kinetic/ potential) energy when it is at its extreme position and has maximum___(kinetic/potential) energy in its mean position.
3) State the True or False . Also correct the false statements.
a) If the displacement is normal to the direction of the force, the work done is negative.
b) When a body is released from a height, the kinetic energy of the body is gradually changed into potential energy.
c) When a body is thrown upwards , the potential energy of the body is gradually transformed into kinetic energy.
d) The change of one form of energy into another form is known as conservation of energy.
4) The following questions are related with an oscillating pendulum, oscillating on either side of its rest position. State whether the following questions of True or False :
a) It has the maximum kinetic energy at its extreme position.
b) it has the maximum potential energy at its rest position.
c) The pendulum has only kinetic energy.
d) The sum of its kinetic energy and potential energy remains constant throughout the motion.
5) Very Short Questions:
1) What are the conditions under which no work is done by a force acting on a body ?
2) Is work a scalar or vector quantity ?
3) In which case the work done by a force will be maximum:
When the angle between the direction of force and the direction of motion is 90° or 0°?
4) State a angle of a situation where the work done by a force is negative.
5) Give an example when a work done by a force acting on a body zero even though the body gets displaced from its initial position by the application of force.
6) For maximum work what should be the angle between the force in the displacement ?
7) State the SI unit of the energy?
8) Name any two units of the energy other than SI unit.
9) State the angle between the direction of force and the direction of motion of a body so that the work done is 0.
10) Name the physical quantity whose unit is watt.
11) Define the term watt.
12) Difference between work and power.
13) Name the various sources of energy.
14) Is it possible that no transformation of energy takes place even when a force is applied to the body ?
15) A light mass and a heavy mass have equal momentum. Which are have more kinetic energy ?
16) A body is thrown vertically upwards. Its velocity keeps on decreasing. What happens to its kinetic energy as its velocity becomes zero ?
17) On what factor does the kinetic energy of a body depend ?
18) What happens to the kinetic energy of a body when the:
a) mass of the body is double at constant velocity.
b) velocity of the body is doubled at constant mass ?
c) mass of the body is doubled but the velocity is reduced to half ?
19) When a stone is thrown a vertically upwards, its velocity goes and decreasing. What happens to its potential energy as its velocity becomes zero ?
20) What kind of energy is possessed by the following:
a) a flying aeroplane:
b) a ceiling fan in the office spring:
c) a compressed spring :
d) A streched rubber band:
e) a man climbing a hill :
f) A running car:
21) While the following are in use, State the energy changes:
a) A the steam engine:
b) A loud speaker :
c) burning coal :
d) A solar cell :
e) petrol or diesel engine automobile :
f) A washing machine:
22) A cell convert one form of energy into another. Name the two forms.
23) What kind of energy transformation takes place at a hydroelectric power station ?
24) What kind of energy transformation take place at a thermal power station ?
25) State the energy changes that takes place when a car at rest starts, accelerates and stopes on the application of breaks.
26) What is the SI unit of work ?
27) How much is the work done by a body when it moves over a complete circular path ? Give reason for your answer.
28) Name the physical quantities for which the following are used as units.
a) kilowatt b) kilowatt-hour
29) A truck driver starts off with his loaded track. What are the major energy changes that take place in setting the truck into motion ?
30) State the energy changes in an oscillating pendulum.
31) Express 1 kWh in terms of SI unit of energy.
32) Which physical quantity does the electron volt measure ? How is it related to the SI unit of this quantity ?
33) What should the angle between force and displacement be to get the:
a) minimum work ?
b) maximum work ?
34) Name the chief energy transformation that occurs:
a) in a lot speaker :
b) in an electric cell (primary):
6) Short Questions:
1) In which of the following cases, is the work being done ?
a) a man pushing a wall
b) A coolie standing with a load of 12kg on his head.
c) a boy climbing a staircase.
d) a boy carrying a box on his head and moving on a frictionless horizontal surface.
2) The sign of the work done by a force on a body is important to understand. State carefully if the following quantities are positive or negative:
a) work done by a man in lifting a bucket out of well by means of rope tied to the bucket.
b) Work done by gravitational force in the above case.
c) Work done by friction on a body sliding down an inclined plane.
d) Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity.
e) Work done by resistivity force of air on a vibrating pendulum in bringing it to a rest.
3) a) Define the term power.
b) How is power related to force and velocity ?
c) What do you understand by the term 'horsepower'? Express it in SI system.
4) What is meant by energy? State its unit. How is energy related to power?
5) Give one relevant example for each of the following transformation of energy :
a) kinetic energy to potential energy.
b) mechanical energy to heat energy
c) mechanical energy to electrical energy
d) electrical energy to heat energy and then to light energy.
e) chemical energy to electrical energy
f) sound energy to electrical energy
g) electrical energy to mechanical energy.
6)a) Define one watt and 1 kWh.
b) converts ¹ kWh into joule.
7) Write an expression for the work done by a constant for acting on a body which gets displaced from its initial position in a direction different from the direction of the force.
b) Give an example when work done by a force acting on a body is zero even though the body gets displaced from its initial position by the application of force.
8) State the principle of conservation of energy.
OR
State the law of conservation of energy.
9) Define
a) i) work ii) power iii) energy
b) How is work done related to the applied force?
c) By what factor does the kinetic energy of a moving body change when its speed is reduced to half ?
d) From the ground floor, a man comes up to the fourth floor of a building using the staircase. Another person comes up to the same floor using an elevator. Neglecting friction, compare the work done in the two cases.
7) Multiple Choice Questions
1) When work is done on a body:
a) it gains energy b) it loses energy c) its remains constant d) none
2) A man pushes a wall but fails to displace it. He does:
a) negative work b) positive work c) no work d) maximum positive work
3) The work done by a force on a body will be positive if the:
a) a body does not a move b) body moves perpendicular to the direction of the applied force c) body moves along the direction of the applied force d) body moves opposite to the direction of the applied force.
4) The power of a body which is doing work at the rate of 1 joule per second is:
a) 10W b) 1W c) 2W d) 5W
5) Power is:
a) the energy needed to move an object b) force x distance c) work x acceleration d) the rate of doing work
6) The SI unit(watt) of a power is equivalent to :
a) kgm/s² b) kg m²/s² c) kg m²/s d) none
7) If a force is applied on a body and it moves with a velocity c, the power will be:
a) F x v b) F/v c) F/v² d) F x v²
8) a calibrated spring balance will be used anywhere in the universe to correctly measure:
a) weight in N b) weight in kg c) mass in N d) mass in g.
9) When a body falls freely:
a) its P. E is converted into K. E
b) its K. E is converted into P. E
c) its mechanical energy is converted into heat energy. d) none
10) A body at rest may possess :
a) kinetic energy b) potential energy c) momentum d) none
11) When the speed of a moving object is doubled, its :
a) accelerations is doubled b) weight is doubled c) kinetic energy is doubled d) kinetic energy increases 4 times.
12) The unit of energy is:
a) newton b) watt c) metre/second d) joule
13) When a body is projected in a gravitational field:
a) its K. E increases b) its P. E increases c) its total energy increases d) its Total energy remains same
14) kinetic energy of an object is proportional to:
a) its velocity b) its weight c) its momentum d) the square of its velocity
15) An electrical motor lifts a 8 kg box vertically through 2.5 m in 10 second. The power produced by the motor is :
a) 0.32W b) 3.2W c) 3.0W d) 20W
16) A pendulum is oscillating on either side of its rest position. Pick out the correct statement:
a) it has only kinetic energy.
b) It has the maximum kinetic energy at its extreme position
c) it has the maximum potential energy at its rest position
d) The sum of its kinetic and potential energy remains constant throughout the motion.
17) If the mass of a body is halved and its velocity is doubled , the kinetic energy of the body:
a) gets doubled b) gets 4 times c) gets 8 times d) remains unchanged
18) a car is running at a speed of 15 kmph while another similar car is moving at a speed of 30 kmph . Their kinetic energies are in the ratio of
a) 1:2 b) 2:1 c) 1:4 d) 4 :1
19) Two bodies with kinetic energy is in the ratio of 4:1 are moving with equal linear momentum. The ratio of their masses is :
a) 1:2 b) 1:1 c) 4:1 d) 1:4
20) A 1 kg mass has a kinetic energy of 1 J when its speed is :
a) 0.45m/s b) 1m/s c) 1.4m/s d) 4.4 m/s
21) The power of a moving body is stored in the form of :
a) work and time b) force and distance c) force and velocity d) distance and acceleration
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