NEET Work Energy and Power MCQs & PYQs

Q: A force of (3ˆi + 4ˆj)N acts on a body and displaced it by (3ˆi + 4ˆj)m . The work done by the force is

By Definition of Work , Work Done = F.S= (3ˆi + 4ˆj).(3ˆi + 4ˆj)= 9+16 =25 J

Q: A 1 kg mass has a kinetic energy of 1 joule when its speed is :

Kinetic Energy K = ½mv² So, 1J = ½(1)v² so, v= √2 m/s= 1.414 m/s

Q: When the velocity of a body is doubled :

Momentum of an object is P = m.v So, when velocity is doubled momentum also doubles

Q: An engine pumps 400 kg of water through height of 10 m in 40 s. Find the power of the pump (g = 10 m/s²).

Power = Work Done / Time Taken Here , Work Done = 400 ×10 ×10 J = 40000 J Time Taken = 40 sec , So, Power = 40000/40 = 1000 W= 1 KW

Q: A force F = (iˆ + ˆj + 2kˆ) N is acting on a particle moving with constant velocity v = (iˆ + ˆj + kˆ) m/s. Power delivered by force is

Power is dot product of Force and Velocity P = F.v ⇒ P= (iˆ + ˆj + 2kˆ). (iˆ + ˆj + kˆ)= 1+1+2= 4 watt

Q: A body is released from position A as shown in figure. The speed of body at position B is

From Principal of Conservation of Energy Ui + Ki= Uf+ Kf ⇒ mg(50) + 0 = mg(10) + ½ m v² ⇒ v² = 800 ⇒ v = 20√2 m/s

Practice NEET Work Energy and Power Questions

Question 1:

easy

A force of (3ˆi + 4ˆj)N acts on a body and displaced it by (3ˆi + 4ˆj)m . The work done by the force is

By Definition of Work ,

Work Done = F.S= (3ˆi + 4ˆj).(3ˆi + 4ˆj)= 9+16 =25 J

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Question 2:

easy

When the bob of a simple pendulum swings, the work done by tension in the string is

As Angle between tension force and displacement is 90°. Work done is zero

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Question 3:

easy

A 1 kg mass has a kinetic energy of 1 joule when its speed is :

Kinetic Energy K = ½mv²

So, 1J = ½(1)v² so, v= √2 m/s= 1.414 m/s

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Question 4:

easy

When the velocity of a body is doubled :

Momentum of an object is P = m.v

So, when velocity is doubled momentum also doubles

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Question 5:

easy

A cubical vessel of height 1 m is full of water. The minimum work done in taking water-out from vessel will be

As side length of cubical tank is 1 m. Volume is 1 m³. Volume of water in 1 m³ is 1000 lit and mass will be 1000 kg.

Height of center of mass of the tank will be 1/2 m.

Potential Energy = 1000 ×10 × 1/2 = 5000 J

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Question 6:

easy

Select correct statement regarding stable equilibrium

All the statements are true regarding stable equilibrium

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Question 7:

easy

An engine pumps 400 kg of water through height of 10 m in 40 s. Find the power of the pump (g = 10 m/s²).

Power = Work Done / Time Taken

Here , Work Done = 400 ×10 ×10 J = 40000 J

Time Taken = 40 sec , So,

Power = 40000/40 = 1000 W= 1 KW

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Question 8:

easy

A force F = (iˆ + ˆj + 2kˆ) N is acting on a particle moving with constant velocity v = (iˆ + ˆj + kˆ) m/s. Power delivered by force is

Power is dot product of Force and Velocity

P = F.v

⇒ P= (iˆ + ˆj + 2kˆ). (iˆ + ˆj + kˆ)= 1+1+2= 4 watt

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Question 9:

easy

A body is released from position A as shown in figure. The speed of body at position B is

From Principal of Conservation of Energy

Ui + Ki= Uf+ Kf

⇒ mg(50) + 0 = mg(10) + ½ m v²

⇒ v² = 800

⇒ v = 20√2 m/s

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Question 10:

easy

A mass m slips along the wall of a hemispherical surface of radius R. The velocity at the bottom of the surface is

From Principal of conservation of Energy in absence of non-conservative forces,

Ui+ Ki= Uf+ Kf

mgR+0= 0+ ½mv²

v= √2gR

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