## October 26, 2012

### CHAPTER 4 :Work and Energy

(1)               Work done will be maximum if the angle between the force F and
displacement d is.

(a)  45o
(b)  90 o
(c)  180 o
(d)   0 o

(2)        A field in which the work done in a moving a body along closed path is zero is called.

(a)  electric field
(b)  conservative field
(c)  electromagnetic field
(d)  maximum
(3)        When a force is parallel to the direction of motion of the boyd, then work done on the body is.

(a)  zero
(b)  minimum
(c)  infinity
(d)  maximum

(4)        Which of the following types of force can do no work on the particle on which it acts?

(a)    frictional force
(b)   gravitational force
(c)    elastic force
(d)   centripetal force

(5)               If a body a mass of 3 kg is raised vertically through 2m, then the work done will be.

(a)    38. 2 J
(b)   392.1 J
(c)    39.2J
(d)   3.92J

(6)               An elevator weighing 3.5 x 10-6 N is raised to a height of 1000 m in the absence of friction, the work done.

(a)  3.5 x 103 J
(b)  3.5 x 104 J
(c)  3.5 x 106 J
(d)  3.5 x 109 J

(7)        The average power and instantaneous power become equal if work is done at.

(a)  any rate
(b)  at variable rate
(c)  at uniform rate
(d)  at high rate

(8)        The relation between horse power and watt is.

(a)  1 hp = 546 watts
(b)  1 hp = 746 watts
(c)  1 hp = 1000 watts
(d)  1 hp = 946 watts

(9)        Proton, electron, neutron and a particles have same momentum. Which of them have highest K.E?

(a)  proton
(b)  electron
(c)  neutron
(d)  a-particle

(10)      Slope of work time graph is equal to.

(a)  displacement
(b)  acceleration
(c)  power
(d)  energy

(11)      Work done by variable force is determine by dividing.

(a)  force into small interval
(b)  displacement into small interval
(c)  both force and displacement into small intervals
(d)  force into small and displacement into large intervals

(12)      Work done on the body equals to the.

(a)  change in its K.E always
(b)  change in its P.E always
(c)  change in it K.E and change in its P.E
(d)  neither change in K.E nor change in its P.E

(13)      The escape velocity of a body in gravitational field of earth is independent of.

(a)  its mass
(b)  the angle at which its is thrown
(c)  both its mass and the angle at which it is thrown
(d)  gravitational field of earth

(14)      The tides raise the mater in the see roughly in a day.

(a)  once
(b)  twice
(c)  four time
(d)  eight time

(15)      The source of geothermal energy is.

(a)  decay of radioactive element in the earth
(b)  compression of material in the earth
(c)  residual lost of the earth
(d)  all as said in a, b and c

(16)      The highest value of escape velocity in solar system is for planet .

(a)  Earth
(b)  Neptune
(c)  Jupiter
(d)  Moon

(17)      Work done by the force of friction is.

(a)  always positive
(b)  always negative
(c)  positive only for small frictional force
(d)  positive only for large frictional force

(18)      P.E of a body has.

(a)  no formula
(b)  a formula mgh only
(c)  a formula
(d)  no general formula

(19)      If velocity is double, then.

(a)  momentum increase 4 times and K.E increases 2 times
(b)  momentum and K.E remain same
(c)  momentum increases 2 times and K.E increase constant
(d)  momentum increases 2 times and K.E increases 4 times

(20)      When the speed of a moving body is doubled, then.

(a)  its K.E is doubled
(b)  its acceleration is doubled
(c)  its P.E is doubled
(d)  its momentum is doubled

(21)      One mega watt hour is equal to.

(a)  36x 106 J
(b)  36x 1012 J
(c)  36x 109 J
(d)  36x 108 J

(22)      Which of the following is not conservative force.

(a)  Friction
(b)  electric
(c)  gravitational
(d)  magnetic

(23)      Work has the dimension as that of same as that of.

(a)  torque
(b)  angular momentum
(c)  linear momentum
(d)  power

(24)      The consumption of energy by a 60 watt bulb in 2 sec is.

(a)  120 J
(b)  60 J
(c)  30 J
(d)  0.02 J

(25)      The relation between the escape velocity Vesc and orbital speed Vo is given by.

(a)  Vesc = 1 /2Vo
(b)  Vesc = √2 Vo
(c)  Vesc = Vo
(d)  Vesc = 2Vo

(26)      The escape velocity form the earth surface in km s-1 is.

(a)  4.2 km s-1
(b)  7.5 km s-1
(c)  9.5 km s-1
(d)  11 km s-1

(27)      If moon radius is 1600 km and g on its surface is 1.6 ms-2, then the escape velocity on the moon is.

(a)  1600 ms-1
(b)  50.6 ms-1
(c)  71.6 ms-1
(d)  2263 ms-1

(28)      When two protons are brought together.

(a)  Kinetic energy increases
(b)  P.E between them increases
(c)  P.E between them decreases
(d)  P.E between them do not change

(29)      When arrow is released from its bow, its energy is transformed from.

(a)  heat energy to K.E
(b)  elastic P.E to K.E
(c)  chemical energy to elastic P.E
(d)  K.E to elastic P.E

(30)      A man lifts, vertically, a weight of 40 kg through 1m in 10s: while a child lifts, vertically, a weight of 10 kg through a distance of 1m in 1s. What will be correct inference?

(a)  man does more than child
(b)  child does more work than man
(c)  both do the same amount of work
(d)  it is a foolish question.

(31)      A man carries a 1 kg suitcase 10 m horizontally across the corridor and then goes up the stairs of total height 10 m. The work done by the man is

(a) 0 J                          (b) 4.9 J
(c) 196 J                      (d) 98 J

(32)      A 100 kg car starting from rest runs down a 30o slope. If the total length of the slope is 20 m, the speed of the car at the bottom, ignoring friction, is

(a) 14000 m/sec     (b) 1.4 m/sec
(c)  20 sin 30o m/sec    (d)  14 m/sec

(33)      A  2m tall man standing at the top of a 30 m tall tower raises a 1 kg mass 0.5 m above his head. The potential energy of the raised mass may be considered to be

(a) 4.9 J                       (b)  24.5 J
(c) 316.5 J                   (d)  all of the above

(34)      A body is falling freely under gravity from point A to point B. The energy of the body at the point C is

(a)     is less than its energy at A
(b) is equal to its energy at A
(b)    is grater than its energy at A
(d) none of these
(35)      When two protons are brought closer together, the P. E. between them

(a) remains constant      (b)  increases
(c)  decreases               (d)  approaches zero

(36)      If a car is moving at a constant speed of 25 m/sec and the total frictional forces acting on it amounts to 1000 N, then the engine power of the car is

(a) 250 joule sec-1        (b) 2500 watt
(c) 25 k watt                (d) 500 k watt

(37)      If you weigh 500 N and in 5 seconds you can run up a flight of stairs consisting of 40 steps, each 15 cm high,  what is your power?

(a) 3000 J                    (b) 3000 J sec-1
(c) 600 watt                 (d)  60 kilowatt

(38)      One horsepower equals

(a) 273 W                    (b) 746 W
(c) 500 W                    (d) 1 kilowatt

(39)      The horse-power required to pump up 2500 kg of water up 100 m in 5 minutes is:

(a) 10.9 hp                   (b) 25 hp
(c) 15 hp                      (d) 5 hp

(40)      Water falls over a fall of 30 m at a rate of 45 3106 kg/min. The power generated is:

(a) 200 MW                 (b) 210 MW
(c) 220 MW                 (d) 230 MW