CBSE Questions for Class 9 Physics Work And Energy Quiz 13 - MCQExams.com

Write true or false for the following statements:
Work and energy have different units.
  • True
  • False
When a stone of mass 'm' falls through a vertical height 'd', the decrease in the gravitational energy is:
  • $$mg/d$$
  • $$mg^2/2$$
  • $$mgd$$
  • $$md/g$$
Write true or false for the following statements:
Kilowatt hour is the unit of power.
  • True
  • False
An object of mass $$5 \,kg$$ falls from a height of $$5 \,m$$ above the ground. The loss of potential energy of the mass is:
  • $$250 \,J$$
  • $$25 \,J$$
  • $$2.5 \,kJ$$
  • $$50 \,J$$
Write true or false for the following statements:
When energy changes from one form to another, the energy that disappears from one form, reappears in exactly equivalents amount in the another form.
  • True
  • False
When a body is falling on the ground from some height, the principle of conservation of energy is violated.
  • True
  • False
A car is accelerated on a leveled road and attains a velocity $$4$$ times its initial velocity. In this process, the potential energy of the car:
  • Does not change
  • Becomes twice to that of initial
  • Becomes $$4$$ times that of initial
  • Becomes $$16$$ times that of initial

    1. State whether the following statement are true or false:

    A machine performs work by itself. 
  • True
  • False
Write true or false for each statement
A gum bottle lying on a table has no energy.
  • True
  • False
When a boy triples his speed, his kinetic energy becomes 
  • half
  • double
  • nine times
  • no charge
The energy of a flying kite is kinetic energy.
  • True
  • False
The energy stored in water of a dam is the kinetic energy.
  • True
  • False
The $$S.I. $$ unit of work is 
  • second
  • metre
  • joule
  • newton
Two coolies $$ A $$ and $$B$$ do same work in time $$ 1$$ minute and $$ 2 $$ minute respectively. The power spent is  
  • same by both coolies
  • is more by coolie $$A$$ than by $$ B $$
  • is less by coolie $$A $$ than by $$B$$
  • nothing can be said.
A body at rest may have 
  • Energy
  • Momentum
  • Speed
  • Velocity
If the stone is thrown up vertically and return to ground, its potential energy is maximum 
  • During the upward journey
  • At the maximum height
  • During the return journey
  • At the bottom
The decrease in the potential energy of a ball of mass $$ 20 kg $$ which falls from a height of $$ 50 cm  $$ is  
  • $$ 968 J $$
  • $$ 98 J $$
  • $$ 1980 J$$
  • None of these
Chose one or more correct alternatives.  Joule is the unit of ____
  • Force
  • Work
  • Power
  • Energy
A man does a given amount of work in 10 sec. Another man does the same amount of work in 20 sec. The ratio of the output power of first man to the second man is
  • $$ 1 $$
  • $$ 1 / 2 $$
  • $$ 2/ 1$$
  • None of these
A force applied by an engine of a train of mass $$ 2.05 \times 10^6  \ kg $$  changes it velocity from $$ 5 \ m /s $$ to $$ 25\ m/s $$  in $$ 5\ minutes$$. The power of engine is 
  • $$ 1.025 \ MW $$
  • $$ 2.05 \ MW $$
  • $$ 5 \ MW $$
  • $$ 6 \ MW $$
If velocity of a body is twice of previous velocity, then kinetic energy will become
  • $$ 2 $$ times
  • $$ \frac{1}{2} $$ times
  • $$ 4 $$ times
  • $$ 1$$ times
A car of mass 1000 kg accelerates uniformly from rest to a velocity  of 54 km/hour in 5s. The average power of the engine during this period in watts is (neglect friction)
  • $$ 2000 \quad W $$
  • $$ 22500 \quad W $$
  • $$ 5000 \quad W $$
  • $$ 2250 \quad W $$
An electric lamp is marked $$60 \ W$$, $$230 \ V$$. The cost of $$1 \ kilowatt-hour$$ of power is $$Rs \ 1.25$$. The cost of using this lamp for $$8 \ hours$$ is
  • $$Rs. \ 1. 20$$
  • $$ Rs. \ 4. 00$$
  • $$Rs. \ 0. 25$$
  • $$Rs. \ 0. 60$$
The power of pump, which can pump $$200 \ kg$$ of water to a height of $$50 \ m$$ in $$10 \ sec$$, will be
  • $$ 10 \times 10^3 \quad watt $$
  • $$ 20 \times 10^3 \quad watt $$
  • $$ 4 \times 10^3 \quad watt $$
  • $$ 60 \times 10^3 \quad watt $$
The spring will have maximum potential energy when 
  • it is pulled out
  • it is compressed
  • both (a) and (b)
  • neither (a) nor (b)
Kilowatt hour is unit of
  • Energy
  • Power
  • Impulse
  • Force
When spring is compressed its potential energy........
  • Remains constant
  • Reduces
  • Increases
  • Nothing can be said about it.
Masses of two bodies are $$1$$ kg and $$4$$ kg respectively. If their kinetic energies are in $$2:1$$ proportion, the ratio of their speeds is .........
  • $$2\sqrt{2}:1$$
  • $$1:\sqrt{2}$$
  • $$1:2$$
  • $$2:1$$
Calculate the energy possessed by a stone of mass $$10\ kg$$ kept at a height of $$5\ m$$. 
Take $$g = 9.8\ m/s^{2}$$
  • $$196\ J $$
  • $$49\ J $$
  • $$490\ J $$
  • $$980\ J $$
A pile driver drives postes into the ground by repeatedly dropping a heavy object on them. Assume the object is dropped from the same height each time. By what factor does the energy of the pile driver-Earth system change when the mass of the object being dropped is doubled?
  • $$\dfrac{1}{2}$$
  • $$1$$; the energy is the sane
  • $$2$$
  • $$4$$
0:0:1


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