Mechanics (Mass, Motion, Force, Acceleration, Momentum, Work, Power, Energy)

Mechanics

(Mass, Motion, Force, Acceleration, Momentum, Work, Power, Energy)

Total Questions: 40

11. Energy conservation means - [M.P.P.C.S. (PRE) 2000]

(a) Generation and destruction of energy.
(b) Energy could be created.
(c) Energy could not be created but destroyed.
(d) Energy can neither be created nor be destroyed.

Correct Answer: (d) Energy can neither be created nor be destroyed.

Solution:The law of conservation of energy states that energy can neither be created nor be destroyed,rather it can only be transformed or transferred one form to another.

12. Most of the source of energy we use represent stored solar energy.Which of the following is not the ultimately derived from the sun,s energy? [U.P.P.C.S. (PRE) 2022]

(a) Nuclear energy
(b) Thermal energy
(c) Biomass energy
(d) Wind energy

Correct Answer: (a) Nuclear energy

Solution:

The thermal energy is stored in the rocks and fluids in the Centre of the earth. Nuclear energy is form of energy released from nucleus the core of atoms made up of neutrons and protons. This source of energy produced by two ways fission and fusion. Hence the nuclear energy is not derived from the sun. Biomass and wind energy are ultimate source of the sun energy.

13. The energy of wind is - [Uttarakhand Lower sub.(pre) 2010]

(a) Only potential energy
(b) Only kinetic energy
(c) Kinetic and potential both
(d) Electrical

Correct Answer: (b) Only kinetic energy

Solution:All moving thing have kinetic energy .It is possessed by an object due to its motion or movement. Wind energy is the kinetic energy of air in motion.The kinetic energy of the wind can be converted into mechanical and electrical energy.

14. In wind power which form of energy converted into electrical energy? [U.P.P.C.S. (pre) 2016]

(a) Kinetic energy
(b) Potential energy
(c) Solar energy
(d) Radiant energy

Correct Answer: (a) Kinetic energy

Solution:The wind is used to generate mechanical power or electricity.Wind turbines convert the kinetic energy of the wind into mechanical power.This mechanical power can be used for tasks such as grinding pumping of water or a generator can convert this mechanical power into electricity.

15. Which of the following energy changes involves frictional force? [68th B.P.S.C.(PRE) 2022]

(a) Kinetic energy to heat energy.
(b) Potential energy to sound energy.
(c) Chemical energy to heat energy.
(d) None of the above.

Correct Answer: (a) Kinetic energy to heat energy.

Solution:Frictional force apply in static condition as well as in a moving condition . The respective of coefficient of friction are called static friction coefficient and dynamic coefficient . While in the static condition there is no displacement no work done and hence no energy conversion. It is in the dynamic condition, there is a movement against the frictional force that there is energy loss by the way of heat. In other words kinetic energy of movement is converted into heat. Energy conversion due to frictional does not change the chemical and potential energy.

16. Match List-1 and List-2 and choose the correct answer from the code given below - [U.P.P.C.S.(mains)2002]

List-1 (Energy conversion)	List-2 (device/ mechanism)
Light to electric	Car braking
Electric to sound	Nuclear reactor
Mass to heat	Loudspeaker
Chemical to heat and light	Solar cell
	Fuel combustion

code :

	A	B	C	D
a)	1	2	3	4
b)	4	3	2	5
c)	2	1	3	5
d)	3	1	2	4

Correct Answer: (b)

Solution:

light to electric - solar cell
electric to sound - loudspeaker
nuclear reactor - mass to heat
fuel combustion - chemical to heat and light
car braking - This involves the conversion of kinetic energy to heat through friction. While not explicitly listed, it's a common energy conversion.

17. Who is the first person to define speed? [67th B.P.S.C.(PRE)(RE.EXAM) 2022]

(a) Galileo
(b) Kepler
(c) Newton
(d) Ptolemy

Correct Answer: (a) Galileo

Solution:Italian physicist Galileo Galilei is usually credited with being the first to measure speed by considering the distance covered and the time it takes. Galileo defined speed as the distance covered per unit of time. In the equation form that is v=d/t (where v is speed and d is distance and t is time). After that Newton pronounced the laws of motion to describe the motion of bodies and objects.

18. Newton first law of motion is known as : [Chhattisgarh P.C.S.(PRE) 2019]

(a) Gravity
(b) Law of inertia
(c) Vertical motion
(d) Law of conservation of momentum

Correct Answer: (b) Law of inertia

19. As the train starts moving the head of the passenger sitting inside the train leans backward because of - [U.P.U.D.A/L.D.A.(PRE)2010]

(a) Inertia of rest
(b) Inertia of motion
(c) Movement of inertia
(d) Conservation of mass

Correct Answer: (a) Inertia of rest

Solution:Newton first law of motion is also known as law of inertia.It states that ,if an object is an rest or moving at a constant speed in a straight line ,it will remain at rest or keep moving in a straight line at constant speed unless acted upon by an unbalanced force.Inertia is the tendency for an object to remain in a state of rest or uniform motion unless a force acts upon it.When a train suddenly starts the passengers tends to fall backwards.This is because the lower part of the body which is an contact with the train begins to move while the upper part of the body tends to maintain its position
due to inertia of rest.As a result, the upper part tends to fall backward.

20. A bus is moving along in straight line and takes a sharp turn to right side suddenly.the passengers sitting in the bus will: [68th B.P.S.C. (PRE) 2022]

(c) bent towards left side
(a) bent towards left side
(b) fall in the forward direction
(d) none of the above

Correct Answer: (c) bent towards left side

Solution:If a bus is moving along a straight path and takes a sharp turn to the right side suddenly then the passengers sitting o the bus will bend towards the left side.Initially the passengers and the bus both are moving in the same direction takes a right turn the lower portion of passengers who are in contact with the bus tends to move in that direction but the upper portion of the passengers will be thrown towards the left.This is because of inertia of direction.

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