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

Two spring of spring constant k and 3k are stretched separately by same force. The ratio of the potential energy stored in them respectively will be 
  • 3 : 1
  • 9 : 1
  • 1 : 3
  • 1 : 9
Which of the following is an example of zero work even when the body suffers a displacement from its initial position?
  • A coolie carrying a load on his head and moving forward on a horizontal road
  • A fielder catching a ball
  • A child pushes a wall
  • A child pulling a toy car
A crane pulls up a car of mass $$500kg$$ to a vertical height of $$4m$$. So, work done by the crane is:
  • $$19.6J$$
  • $$19.6kJ$$
  • $$19600kJ$$
  • $$4900J$$
Watt hour represents:
  • Electric energy
  • Current
  • Voltage
  • Power
Unit used in selling electrical energy to consumer is:
  • $$Volt-Ampere$$
  • $$Kilowatt-hour$$
  • $$Volt/second$$
  • None of these
A lamp rated $$20W$$ and an electric iron rated $$50W$$ are used for $$2$$ hour everyday. Calculate the total energy consumed in $$20 $$ days.
  • $$14kwh$$
  • $$2.8kwh$$
  • $$40kwh$$
  • None of these
Number of KWh in 1 Joule.
  • $$\displaystyle 3.6\times { 10 }^{ 6 }\ KWh$$
  • $$\displaystyle 2.77\times { 10 }^{ -7 }\ KWh$$
  • $$\displaystyle 600\ KWh$$
  • $$\displaystyle 1.6\times { 10 }^{ -19 }\ KWh$$
Which of these units of energy is the largest?
  • $$1\ Calorie$$
  • $$1\ Joule$$
  • $$1\ Erg$$
  • $$1\ Kilowatt-hour$$
Calculate the power of a source if it produces energy of $$250\ J$$ in $$10\ s$$.
  • $$2500\ W$$
  • $$2.5\ W$$
  • $$25\ W$$
  • Zero
Convert 1 kWh to SI unit of energy.
  • $$3.6\times 10^6J$$
  • $$3.6\times 10^8J$$
  • $$1.8\times 10^6J$$
  • $$1.8\times 10^8J$$
Energy consumed in our house has a unit of
  • watts
  • horse power
  • kilowatt-hours
  • none
In which form, the energy is stored in a fuel?
  • Potential energy
  • Thermal energy
  • Kinetic energy
  • Chemical energy
Which one of the following energies cannot be possessed by a body at rest?
  • Potential energy
  • Kinetic energy
  • Thermal energy
  • Magnetic energy
A freely falling object eventually stops on reaching ground. What happens to its potential and kinetic energy while falling?
  • Potential energy decreases and Kinetic energy increases
  • Potential energy increases and Kinetic energy increases
  • Potential energy increases and Kinetic energy decreases
  • None
What is practical unit of power?
  • Watt
  • Kilo watt
  • Horse power
  • None of these
A certain household has consumed $$250$$ units of energy during a month. How much energy is this in joules?
  • $$9 \times 10^{10}\ J$$
  • $$9 \times 10^{8}\ J$$
  • $$9 \times 10^{9}\ J$$
  • $$9 \times 10^{-8}\ J$$
Find energy in kWh consumed in 10 hours by four devices of power $$500\ W$$ each?
  • $$10\ kWh$$
  • $$20\ kWh$$
  • $$30\ kWh$$
  • $$40\ kWh$$
Smallest commercial unit of energy is
  • Kilowatt hour
  • Watt second
  • Watt hour
  • Watt minutes
Convert $$28.8  kJ$$ into kilo watt hour.
  • $$8 \times {10}^{-3} kwh$$
  • $$8 kwh$$
  • $$8 \times {10}^{3} kwh$$
  • None of these
An object is dropped from height $$h=2R$$ on the surface of earth. Find the speed with which it will collide with ground, by neglecting effect of air. [$$R$$ is radius of earth. Take mass of earth as $$M$$]
  • $$2 \sqrt {\dfrac {GM} {3R}}$$
  • $$\sqrt {\dfrac {2GM} {R}}$$
  • $$\sqrt {\dfrac {GM} {R}}$$
  • $$\sqrt {\dfrac {GM} {2}}$$
Calculate the monthly bill if a heater of 100 watt is used at the rate of rs. 1 per unit for 1 hour daily.
  • Rs. 200
  • Rs. 6000
  • Rs. 100
  • Rs. 3
Commercial unit of energy is .......................
  • Joule
  • Volt
  • Kilowatt hour
  • Watt second
What is law of conservation of energy?
  • Energy can neither be created nor destroyed. It can only be transformed from one to another.
  • Energy can only be created nor destroyed. It can only be transformed from one to another.
  • Energy can neither be created but can be destroyed. It can only be transformed from one to another.
  • None
An object of mass $$40\ kg$$ is raised to a height of $$5\ m$$ above ground. If the object is allowed to fall down find its kinetic energy when it is half-way down.
  • 1960 J
  • 980 J
  • 990 J
  • 1000 J
A weight-lifter lifts a weight of $$2000N$$ straight up to a height of $$2.25\ m$$ in $$65$$ seconds. The weight-lifter kept holding the weight at the same height for the next $$4$$ seconds before dropping it to the floor. Find out how much work did the weight lifter do while holding the weights overhead for $$4$$ seconds ?
  • $$1300\ Joules$$
  • $$3077\ Joules$$
  • $$4500\ Joules$$
  • $$8000\ Joules$$
  • No work was done
All types of energy that exist in the nature can be categorized as either kinetic or potential. Choose correct statement regarding the validity of above sentence.
  • This statement is true for thermal and and mechanical, but not elastic
  • This statement is true for all different types of energy
  • This statement is false, except in the case of mechanical energy
  • This statement is never true
A car standing at the top of a hill would be an example of what type of energy?
  • Kinetic
  • Topical
  • Potential
  • Beneficial
  • Residual
Find out work done by a person in pushing a box with a force of $$10\ N$$ over a distance of $$4.0\ m$$ in the direction of the force?
  • $$0.4\ J$$
  • $$4.0\ J$$
  • $$40\ J$$
  • $$400\ J$$
  • $$4000\ J$$
If $$120J$$ of work is done in $$2$$ minutes by a water pump, the power of the pump is:
  • $$14.4\  KW$$
  • $$240\  W$$
  • $$60\  W$$
  • $$1\  W$$
A father holds his child on his shoulders during a parade. The father does no work during the parade because:
  • No force acts on the child
  • The momentum of the child is constant
  • The potential energy of the child is varying
  • The child's kinetic energy is constant
  • The child's distance from the ground remains the same
0:0:1


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