2) State the circumstances under which work done by a body is zero.
3) A body moves in the direction of force applied. Write the expression for work done by it.
4) Write the expression for work, if force and displacement of the body are not along one straight line.
5) Name the units of work in MKS system.
a) fundamental units
b) gravitational units.
6) Define the following :
a) joule
b) kilogram metre.
7) Fill in the blanks.
a) 1 joule = ____Nm.
b) 1 kg m = ____Nm.
8) How do you define power ?
9) Express power in terms of:
a) displacement
b) velocity
10) What are units of power in MKS system?
a) Absolute units.
b) Gravitational units.
11) Match the quantities given below:
S.N Name of units Magnitude
1. newton Js⁻¹
2. joule kg ms⁻²
3. kilogram metre Nm
4. watt 9.8 Nm
12) How do you define:
a) potential energy
b) gravitational potential energy
13) A body of mass 'm' is moved through a height of h in vertically upward direction. Find the change in its potential energy. Express it along with proper units.
14) Name the types of mechanical energy ?
15) How do you define kinetic energy ?
16) Obtain an expression for kinetic energy of a body.
17) Obtain a relation between Kinetic energy and momentum.
18) Show that the momentum of a body varies directly at the square root of the kinetic energy of the body.
19) The list shows different types of energy.
(chemical, electrical , heat, light, Kinetic, nuclear, potential, sound)
Use, only, the words from the list to complete the following sentences . Words may be used more than once or not at all.
a) When a child plays with a battery driven car, ____energy is turned into___ energy as the car moves.
b) When a saying moves, the____energy at the highest point is changed into ____ energy as the swing falls.
c) When a person sings, the ____ energy from their food is turned into ___energy.
d) When a student lights a Bunsen's burner, chemical energy is turned into ____ and___ energy.
e) When a moving car is stopped by the application of brakes, ___energy is converted into ____energy.
20) A force of 5N displaces a body through a distance of 2m in its own direction. Calculate the work done.
21) A force of 10N acts on a body for some time and imparts a velocity of 6 m/s. Calculate the momentum of body if it moves with an acceleration of 2m/s².
22) A force of 8 N acts on a body for 5 second, continuously, on a frictionless plane. Calculate the momentum of the body if the body were at rest initially.
23) A body of mass 5kg moved to a height of 2 m. What is its potential energy ? g= ms⁻².
24) Calculate the kinetic energy of a body of mass 2 kg moving with a velocity of 5 ms⁻¹.
25) A body of mass 2 kg possesses same kinetic energy as that possessed by a body of mass 8 kg moving with a velocity of 5 ms⁻¹. Calculate the velocity of first body.
26) A heavier body and a lighter body possess same kinetic energy. Which of the two has greater momentum ?
27) When a car accelerates up a slope what happens to its kinetic energy and gravitational potential energy ?
28) A body lifts a pail of water of weight 5 kgf through a vertical distance of 2m up a flight of steps. What will be the work done? take g= 10ms⁻².
29) A body weighing 500N runs upstairs from A to B as shown in figure. What work is done against Gravity ?
31) A moving car is slowed down by the application of brakes . State which type of energy is converted into which other type ?
32) A box of weight 300N is pulled 5m along horizontal floor by a a force 10N. It is then lifted vertically through a distance of 2m. What is the total work done on the box ?
33) A simple pendulum swings as shorin figure
b) At which point kinetic energy is maximum ?
c) How does total mechanical energy change during vibrations ?
34) A heavier body and a lighter body possesses same momentum. Which of the two has greater kinetic energy ?
35) Two bodies have their masses in the ratio 4:1. Calculate the ratio of their momentum if they have equal kinetic energies .
36) Two bodies have their masses in the ratio 4:1. Calculate the ratio their kinetic energies if they have equal momentum.
37) A body of mass 'm' is moving with a velocity 'v'. How will its kinetic energy change if the mass of a body is halved and velocity doubled?
38) A gardener uses a plank to move soil in a wheel barrow from a point A to a point B.
b) The garden takes 3 second to push the wheel barrow from A to B. calculate the power developed.
c) Calculate the average speed of the wheel barrow as it is pushed up the plank.
39) Give one example for each of the following:
a) Change in energy due to change in position.
b) Change in energy due to compression .
c) Change in energy due to elongation.
d) Change in energy due to twisting.
40) Give one example, where no work is done in spite of non-zero force and displacement.
41) A man weighing 70 kg carries a box weighing 30 kg on his head. Calculate the work done if,
a) he moves through a distance of 10 m on a horizontal road.
b) he climbs 8 steps on staircase, height of each 0.5 m.
42) A man lifts a weight of 40 kg through a height of 1.5 m in 5 second. Calculate, in watt, power of the man (take g= 10ms⁻²)
43) a) A machine can raise a load of 3000 N through a height of 20m in a time of 15s.
i) Calculate the work done in lifting the load.
ii) What power, in watt, is required to lift at the load ?
b) The machine was tested using different loads. A graph of efficiency verses load was plotted. From the graph, find
b) The load, in newton, for which efficiency 50%.
c) The efficiency when the load is 3000N.
44) An engine pulls a train on a level track with a velocity of 70 kmph by applying a force 15 x 10N. Find the horsepower of the engine (1 H. P= 750 W).
45) Following list contains certain types of energy changes
electrical energy---> light energy
chemical energy---> heat energy
light energy ----> chemical energy
light energy ---> kinetic energy
From this, select the energy changes the occur in each of the following.
a) A motor is switched on
b) Coal is burnt
c) A table lamp is used
d) photosynthesis
e) A kerosene stove
f) An electric fan
46) Complete the table below the show the main type of energy involved.
Device Energy before use Energy when used
a) loudspeaker ____ _______
b) _____ gravitational potential energy kinetic energy
c) microphone _____ _____
d) ____ electric energy kinetic energy
e) Hair dryer _____ ______
47) A model car of weight 2N, runs down the track as shown in fig .
b) What type of energy does the car have when it is stationery at the point A.
c) What is the mass of car ? (Take g= m/s²).
48) A water pump lifts 800 kg of water from a well 15 m deep in 1 minute. Calculate the horse power of the motor. (g= 10m/s² and 1 HP= 750W)
49) State law of conservation of energy.
50) Is there any case where law of conservation of energy is not valid ?
51) State law of conservation of mechanical energy.
52) Give one example explaining the concept of law of conservation of mechanical energy.
53) A body is dropped from a height 'h'. At any instant , it is at a distance x from the top.
a) Prove that the total mechanical energy of the body when the payment of x.
b) What is the net mechanical energy at that instant ?
54) A ball rolling on the ground, comes to rest after sometime. What happens to its kinetic energy ?
55) Fill in the two blanks columns of following table.
S.N Case Type of energy fed Type of energy emitted
1. Burning wood _____ _____
2. Rotating fan _____ _____
3. Room heater _____ _____
4. Bulb _____ _____
5. Microphone _____ _____
56) Name the device based upon conversion of electrical energy to mechanical energy?
57) Name the device based upon conversion of mechanical energy to electrical energy.
58) Name the device which converts light in to electricity.
59) Give an example where chemical energy is converted into heat.
60) What type of energy is, first of all, given to simple pendulum.
61) After some time a vibrating simple pendulum stops. What happens to the energy given to it ?
62) What is the type of energy contained in the simple pendulum when it is
a) in mean position
b) at extreme position.
63) At which point does a vibrating simple pendulum possess maximum energy.
a) At a mean position. yes/no
b) At extreme position yes/no
c) Same energy every where yes/no
64) f7ill in the blanks:
a) Absolute unit work in MKS system is ____
b) Gravitational unit of work in MKS system is____
c) 1 kilogram metre is equal to ____ joule.
d) Power is the ratio between___and___ .
e) Potential energy of a body, in CGS system, is expressed in____
f) a battery converts____ energy into electrical energy.
g) The ___energy of wind in a windmill is converted to ___energy in a generator.
h) A solar cell converts___ energy to___ energy.
i) a lamp converts electrical energy into___ energy.
j) a thermo-couple converts___ energy into___ energy
k) Kinetic energy of a body varies directly as ____of its velocity.
l) Kinetic energy of a body varies___ as the mass of the body of its momentum is kept constant.
m) In a free fall, law of conservation of _____energy holds good .
n) There is no exception to the validity of law of conversion of ____.
o) a fan converts ---- energy to____ energy.
65) State True or False
a) Work done is always positive.
b) Work done can be zero inspite of the fact that neither force nor displacement is zero.
c) Absolute unit of work is kilogram.
d) 1 Newton metre and joule are same things.
e) a body lying on the surface of the earth may have potential energy.
f) Kinetic energy of a body is directly proportion to the velocity of the body.
g) A dynamo Converts electrical energy to mechanical energy.
h) A microphone Converts vibrational energy in to electrical energy.
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