chap.4 Work and energy MCQs with solution

Work and energy

1)	Area under the curve of force-displacement   graph is equal to:    a) Displacement           b) Work                 c) Power                            d) Energy	B
2)	Slope of work time graph is equal to.    a) Displacement             b) Acceleration       c) Power                            d) Energy	C
3)	Work done will be maximum if the angle   between the force F and displacement d is.    a) 450                                                 b) 900                 c) 1800                                d) 0 0	D
4)	A field will be conservative when work   done: a) By centripetal force is zero      b) By a frictional force is negative c) By force perpendicular to the displacement is zero d) In a close path is zero	D
5)	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	b
6)	When a force is parallel to the direction of   motion of the body, then work done on the   body is:  a) zero                                                b) minimum     c) infinity                            d) Maximum	D
7)	The work done is said to be negative when   force and displacement are    a) Parallel                          b) Anti-parallel               c) Perpendicular               d) None	B
8)	Which of the following is not conservative   force?    a) Friction                          b) Electric                         c) Gravitational                   d) Magnetic	a
9)	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	D
10)	Work has the dimension as that of same as    that of. a) Torque                               b) Angular momentum c) Linear momentum                       d) Power	A
11)	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	C
12)	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	b
13)	If mass of a moving object is doubled, its    K.E becomes:     a) 2 times                       b) 4 times                             c) 5 times                             d) 16 times	B
14)	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.	A
15)	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	B
16)	The consumption of energy by 60 watt bulb         in 2 seconds is:     a) 20 J                               b) 120 J c) 30 J                                   d) 0.02 J	b
17)	Power is also defined as dot product of     a) Force and displacement                         b) Force and mass     c) Force and velocity                                                   d) Force and time	C
18)	One kilowatt hour of work is equal to     a) 0.36 MJ                       b) 3.6 MJ                             c) 36 MJ                               d) 360 MJ	B
19)	One mega watt hour is equal to.     a) 3.6x 106 J                      b) 3.6x 1012 J               c) 3.6x 109 J                      d) 3.6x 108 J	C
20)	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	D
21)	The work done by the force of 10N applied    parallel to direction of motion up to 20 m     a) 10 J                               b) 20 J                                    c) 200 J                                                d) 2000 J	c
22)	The SI unit of power is     a) Joule                            b) Horsepower                    c) kWh                                 d) Watt	D
23)	The original source of tidal energy is:     a) Moon                           b) Earth                                c) Sun                                   d) Sea	A
24)	The energy stored in the spring of a watch    is:     a) K.E                                b) Electrical Energy          c) Elastic P.E                      d) Solar Energy	C
25)	The tides raise the mater in the sea roughly    in a day:     a) Once                             b) Twice                            c) Four times                    d) Eight times	b
26)	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	D
27)	When a force retards the motion of a body, the work done is:    A.Zero B.Negative C.Positive D.+ve or-ve depending upon magnitude of force and displacement	B
28)	The product of pressure and volume has the same SI base units as; A. Energy                            B.Force C.Power                              D.Heat Capacity	A
29)	When a body moves against the force of friction on a horizontal plane, the work zone by the body is; A)  negative       B) positive C) zero                                 D) max and positive	A
30)	An engine pumps out 40 kg of water in second. The water comes out of vertically upward with a velocity of 3 ms the power of engine in kilowatt is; A.1.2 kW             B. 12 kW C.120 kW            D. 1200 kW	A	P =FV = mgV = 40x10x3=-1200= 1.2kW
31)	Two boys weighting in the ratio 4:5 goes up stair taking time in the ratio 5:4. The ratio of their power is;           A. 1                                        B. 1625 C. 25/16                              D. 4/5	B	P1/P2 =  =  =  =  x   = 16/25