NEET Physics Work Energy and Power MCQs Set B

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d) zero

Answer:

Question:  The heart of man pumps 5 litres of blood through the arteries per minute at a pressure of 150 mm of mercury. If the density of mercury be 13.6 ×10³ kg/m³ and g = 10m/s² then the power of heart in watt is :

a) 1.70

b) 1.50

c) 3.0

d) 2.35

Answer:  1.70

Question:   A ball is thrown vertically downwards from a height of 20 m with an initial velocity v₀. It collides with the ground loses 50 percent of its energy in collision and rebounds to the same height. The initial velocity v₀ is :(Take g = 10 ms^–2)

a) 20 ms^–1

b) 10 ms^–1

c) 28 ms^–1

d) 14 ms^–1

Answer: 20 ms^–1

Question:  A particle of mass m is driven by a machine that delivers a constant power of k watts. If the particle starts from rest the force on the particle at time t is

a)

b)

c)

d)

Answer:

Question:   Two similar springs P and Q have spring constants K_P and K_Q, such that K_P > K_Q. They are stretched, first by the same amount (case a,) then by the same force (case b). The work done by the springs W_P and W_Q are related as, in case (a) and case (b), respectively

a)

b)

c)

d)

Answer:

Question:  A block of mass 10 kg, moving in x direction with a constant speed of 10 ms_–1, is subject to a retarding force F = 0.1 × J/m during its travel from x = 20 m to 30 m. Its final KE will be:

a) 475 J

b) 250 J

c) 275 J

d) 450 J

Answer:  475 J

Question:

a)

b)

c)

d)

Answer:

Question:  Figure here shows the frictional force versus displacement for a particle in motion. The loss of kinetic energy in travelling over s = 0 to 20 m will be

a) 250 J

b) 200 J

c) 150 J

d) 10 J

Answer: 250 J

Question:  A particle of mass m moving in the x direction with speed 2v is hit by another particle of mass 2m moving in the y direction with speed v. If the collision is perfectly inelastic, the percentage loss in the energy during the collision is close to :

a) 56%

b) 62%

c) 44%

d) 50%

Answer:  56%

Question:  k is stretched by a small length x. It is further stretched by another small length y. The work done in the second stretching is

a) 1/2 Ky(2x + y)

b) 1/2 k (x + y)²

c) 1/2 Ky²

d) 1/2 K(x² + y²)

Answer:  1/2 Ky(2x + y)

Question:

a) (2t³ + 3t⁵)W

b) (2t² + 4t⁴)W

c) (2t² + 3t³)W

d) (2t³ + 3t⁴) W

Answer: (2t³ + 3t⁵)W

Question:  A particle of mass 10 g moves along a circle of radius 6.4 cm with a constant tangential acceleration. What is the magnitude of this acceleration if the kinetic energy of the particle becomes equal to 8 × 10^–4 J by the end of the second revolution after the beginning of the motion?

a) 0.1 m/s²

b) 0.18 m/s²

c) 0.2 m/s²

d) 0.15 m/s²

Answer:  0.1 m/s²

Question:

a) 0.29 and 3.5 m

b) 0.29 and 6.5 m

c) 0.2 and 6.5 m

d) 0.2 and 3.5 m

Answer: 0.29 and 3.5 m

Question:  A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times. Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up? Fat supplies 3.8 × 107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate. Take g = 9.8 ms^–2 :

a) 12.89 × 10^–3 kg

b) 2.45 × 10^–3 kg

c) 9.89 × 10^–3 kg

d) None of these

Answer:  12.89 × 10^–3 kg

Question:

a) 90°

b) 135°

c) 180°

d) 45°

Answer:  90°

Question:  Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m/s. Take 'g' constant with a value 10 m/s².  The work done by the (i) gravitational force and the (ii) resistive force of air is

a) (i) 10 J (ii) – 8.75 J

b) (i) – 10 J (ii) –8.25 J

c) (i) 100 J (ii) 8.75 J

d) (i) 1.25 J (ii) –8.25 J

Answer:  (i) 10 J (ii) – 8.75 J

Question:   Figure shows three forces applied to a trunk that moves leftward by 3 m over a smooth floor. The force magnitudes are F₁ = 5N, F₂ = 9N, and F₃ = 3N. The net work done on the trunk by the three forces

a) 1.50 J

b) 3.00 J

c) 2.40 J

d) 6.00 J

Answer: 1.50 J

Question: Assertion : Graph between potential energy of a spring versus the extension or compression of the spring is a straight line.
Reason : Potential energy of a stretched or compressed spring, proportional to square of extension or compression

a) If both the Assertion and Reason are incorrect

b) If Assertion is correct but Reason is incorrect

c) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion

d) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion

Answer: If both the Assertion and Reason are incorrect

Question: A time dependent force F = 6t acts on a particle of mass 1 kg. If the particle starts from rest, the work done by the force during the first 1 second will be

a) 4.5 J

b) 22 J

c) 18 J

d) 9 J

Answer:  4.5 J

Question:

a) 10^–4 kg m^–1

b) 10^–3 kg m^–1

c) 10^–1 kg m^–1 s^–1

d) None of these

Answer:  10^–4 kg m^–1

Question:   A particle of mass m moving in the x direction with speed 2v is hit by another particle of mass 2m moving in the y direction with speed v. If the collision is perfectly inelastic, the percentage loss in the energy during the collision is close to

a) 56%

b) 62%

c) 44%

d) 50%

Answer:  56%

Question:

a)

b)

c)

d) D

Answer:

Question:  A moving block having mass m, collides with another stationary block having mass 4m. The lighter block comes to rest after collision. When the initial velocity of the lighter block is v, then the value of coefficient of restitution (e) will be

a) 0.25

b) 0.4

c) 0.8

d) 0.5

Answer: 0.25

Question: Assertion : A quick collision between two bodies is more violent than slow collision, even when initial and final velocities are identical.
Reason : The rate of change of momentum determines that the force is small or large.

a) If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion

b) If both Assertion and Reason are correct and Reason is the correct explanation of Assertion

c) If Assertion is correct but Reason is incorrect.

d) If both the Assertion and Reason are incorrect

Answer:  If both Assertion and Reason are correct, but Reason is not the correct explanation of Assertion

Question:

a) zero

b)

c)

d)

Answer:  zero

Question:   In a collinear collision, a particle with an initial speed v₀ strikes a stationary particle of the same mass. If the final total kinetic energy is 50% greater than the original kinetic energy, the magnitude of the relative velocity between the two particles, after collision, is:

a)

b)

c)

d)

Answer:

Question:   The mass of a hydrogen molecule is 3.32×10^–27 kg. If 10²³ hydrogen molecules strike, per second, a fixed wall of area 2 cm² at an angle of 45° to the normal, and rebound elastically with a speed of 10³ m/s, then the pressure on the wall is nearly:

a) 2.35 × 10³ N/m²

b) 2.35 × 10² N/m²

c) 2.35 × 10⁴ N/m²

d) 2.35 × 10⁵ N/m²

Answer:  2.35 × 10³ N/m²

Question:  It is found that if a neutron suffers an elastic collinear collision with deuterium at rest, fractional loss of its energy is p_d; while for its similar collision with carbon nucleus at rest, fractional loss of energy is P_c. The values of P_d and P_c are respectively:

a)

b)

c)

d)

Answer:

Question:  A particle of mass m₁ moving with velocity v collides with a mass m₂ at rest, then they get embedded. Just after collision, velocity of the system

a) decreases

b) becomes zero

c) increases

d) remains constant

Answer:  decreases

Question:  A block of mass 1 kg is pulled along the curve path ACB by a tangential force as shown in figure. The work done by the frictional force when the block moves from A to B is

a) 20 J

b) 5 J

c) 10 J

d) None of these

Answer:  20 J

Question:

a)

b)

c) infinite

d) n

Answer:

Question:   A mass of M kg is suspended by a weightless string. The horizontal force that is required to displace it untill the string makes an angle of 450 with the initial vertical direction is

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d) zero

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d)

Answer:

Question:    A man of mass m on an initially stationary boat gets off the boat by jumping to the left in an exactly horizontal direction. Immediately after the  jump,the boat of mass M, is observed to be moving to the right at speed v. How much work did the man do during the jump (both on his own body and on the boat)

a)

b)

c)

d) None of these

Answer:

Question:

a) 2A / B

b) A / B

c) B / A

d) B / 2A

Answer:  2A / B

Question:  An electric pump is used to fill an overhead tank of capacity 9m³ kept at a height of 10m above the ground. If the pump takes 5 minutes to fill the tank by consuming 10 kW power the efficiency of the pump should be (g = 10 ms^–2)

a) 30%

b) 20 %

c) 40 %

d) 60 %

Answer:  30%

Question:  A force of 250 N is required to lift a 75 kg mass through a pulley system. In order to lift the mass through 3 m, the rope has to be pulled through 12m. The efficiency of system is

a) 75%

b) 33%

c) 90%

d) 50%

Answer:  75%

Question:  A car of mass m starts from rest and accelerates so that the instantaneous power delivered to the car has a constant magnitude P₀. The instantaneous velocity of this car is proportional to :

a)

b)

c)

d)

Answer:

Question:  A body of mass 5 kg explodes at rest into three fragments with masses in the ratio 1 : 1 : 3. The fragments with equal masses fly in mutually perpendicular directions with speeds of 21 m/s. The velocity of heaviest fragment in m/s will be

a)

b)

c)

d)

Answer:

Question:

a)

b)

c)

d) 1

Answer:

Question:

a) 10 cm

b) 2.0 cm

c) 2.0 cm

d) 1.0 cm

Answer:  10 cm

Question:   A ring of mass m can slide over a smooth vertical rod as shown in figure. The ring is connected to a spring of force constant k = 4 mg / R, where 2 R is the natural length of the spring. The other end of spring is fixed to the ground at a horizontal distance 2 R from the base of the rod. If the mass is released at a height 1.5 R, then the velocity of the ring as it reaches the ground is

a)

b)

c)

d)

Answer: