NEET Physics Work Energy And Power Revision Notes

Question. A force F = (5ˆi + 3ˆj) N is applied over a particle which displaces it from its origin to the point r = (2ˆi − 1ˆj) metres. The work done on the particle is:
a. –7 J
b. +13 J
c. +7 J
d. +11 J
Answer : C

Question. A box of mass 1 kg is pulled on a horizontal plane of length 1 m by a force of 8 N then it is raised vertically to a height of 2m, the net work done is:
a. 28 J
b. 8 J
c. 18 J
d. None of above
Answer : A

Question. A 10 kg satellite completes one revolution around the earth at a height of 100 km in 108 minutes. The work done by the gravitational force of earth will be:
a. 108×100×10 J
b. (108x10/100) J
c. (100 x 10/108) J
d. Zero
Answer : D

Question. A 10 kg mass moves along x-axis. Its acceleration as a function of its position is shown in the figure. What is the total work done on the mass by the force as the mass moves from x = 0 to x = 8 cm:

a. 2 8 x 10⁻² J
b. 2 16 x 10⁻² J
c. 4 x 10⁻⁴ J
d. 1.6 x 10⁻³ J
Answer : A

Question. The graph between the resistive force F acting on a body and the distance covered by the body is shown in the figure. The mass of the body is 25 kg and initial velocity is 2 m/s. When the distance covered by the body is 5m, its kinetic energy would be:

a. 50 J
b. 40 J
c. 20 J
d. 10 J
Answer : D

Question. A position dependent force F = (7−2x+3x²)N acts on a small abject of mass 2 kg to displace it from x = 0 tox = 5m . The work done in joule is:
a. 70 J
b. 270 J
c. 35 J
d. 135 J
Answer : D

Question. A particle moves under the effect of a force F = Cx from x = 0 to x = x₁. The work done in the process is:
a. Cx²₁
b. (1/2)Cx²₁
c. Cx₁
d. Zero
Answer : B

Question. If W₁, W₂ and W₃ represent the work done in moving a particle from A to B along three different paths 1, 2 and 3 respectively (as shown) in the gravitational field of a point mass m, find the correct relation:

a. W₁ > W₂ > W₃
b. W₁ = W₂ = W₃
c. W₁ < W₂ < W₃
d. W₁ > W₂ > W₃
Answer : B

Question. A steel ball of mass 2 m surface one-dimensional elastic collision with a row of three steel balls, each of mass m. If mass 2 m has collided with velocity υ and the three balls numbered 1, 2, 3 were in initially at rest, then after the collision:

a. balls 1, 2 and 3 would start moving to the right, each with velocity υ/3
b. balls 2 and 3 would start moving to the right, each with a velocity υ/2
c. balls 2 and 3 would start moving to the right, each with a velocity υ
d. ball 1 and ball of mass 2 m would remain at rest
Answer : C, D

Question. A ball A of mass m with velocity υ collides head-on with
a stationary ball B of mass m. If e be the coefficient of restitution, then which of the following are correct?
a. The ratio of velocities of balls A and B after the
collision is (1+ e) /(1− e)
b. The ratio of the final and initial velocities of ball A is (1− e) / 2
c. The ratio of velocities of balls A and B after the collision is (1− e) /(1+ e)
d. The ratio of the final and initial velocities of ball B is (1+ e) / 2
Answer : B, C, D

Question. Consider the situation shown in figure.

The block of mass 1.0 kg is released form rest and it is found to have a speed of 0.3 m s^–1 after it has descended through a distance of 1 m. Which of the following are correct? (Take g = 10 m s^–2)
a. Loss in gravitational potential energy is 10 J
b. Kinetic energy of 1 kg block is 0.045 J
c. 4 kg block travels a distance of 2 m to acquire a velocity of 0.6 m s^–1
d. Work done against friction in 80μ joule where μ is coefficient of kinetic friction.
Answer : ALL

Question. A particle of mass 0.01 kg travels along a curve with velocity given by 4iˆ + 16kˆms-1 After some time, its velocity becomes 8iˆ + 20 ˆj ms-1 due to the action of a conservative force. The work done on particle during this interval of time is:
a. 0.32 J
b. 6.9 J
c. 9.6 J
d. 0.96 J
Answer : D

Question. An ice cream has a marked value of 700 kcal. How many kilowatt hour of energy will it deliver to the body as it is digested?
a. 0.81 kWh
b. 0.90 kWh
c. 1.11 kWh
d. 0.71 kWh
Answer : A

Question. A metallic wire of length L metres extends by l metres when stretched by suspending a weight Mg to it. The mechanical energy stored in the wire is:
a. 2Mgl
b. Mgl
c. Mgl/2
d. Mgl/4
Answer : C

Question. Following figure gives force versus time graph. The force is acting on a particle of mass 2.0 kg at rest at t = 0 and particle is moving in one-dimension. Which of the following are correct?

a. The impulse of the force in the time interval t = 8 s to t = 12 s is –10 N-s
b. The velocity change in the interval t = 8 s to t =10 s is – 15 m s^–1
c. The kinetic energy of the particle at t = 6 s is 2500 J
d. The kinetic energy of the particle at t = 6 s is 500 J
Answer : A, B, C

Question. The figure given below shows how the net interaction force between two particles A and B is related to the distance between them. When the distance between them varies from x₁ to x₄, then:

a. Potential energy of the system increases from x₁ to x₂
b. Potential energy of the system increases from x₂ to x₃
c. Potential energy of the system increases from x₃ to x₄
d. Kinetic energy increases from x₁ to x₂ and decreases from x₂ to x₃
Answer : B, C, D

Question. If m, p, and t denote respectively the mass, linear momentum and angular momentum of a particle moving on a circle of radius r, then the kinetic energy of the particle can be expressed as:
a p²/2m
b. l²/2m
c. p²/2mr²
d. l²/2mr²
Answer : A, B

Question. A ball moves over a fixed track as shown in figure. From A to B, the ball rolls without slipping. Surface BC is frictionless K_A K_B, and K_C are kinetic energies of the ball at A, B and C respectively. Then:

Answer : A, B

Question. A rope ladder with a length l carrying a man with a mass m at its end is attached to the basket of balloon with a mass M. The entire system is in equilibrium in the air. As the man climbs up the ladder into the balloon, the balloon descends by a height h. Then the potential energy of the man:
a. increases by mg (l − h)
b. increases by mg l
c. increases by mg h
d. increases by mg (2l − h)
Answer : A

Question. A stone tied to a string of length L is whirled in a vertical circle with the other end of the string at the centre. At a certain instant of time, the stone is at its lowest position, and has a spend u. The magnitude of the change in its velocity as it reaches a position, where the string is horizontal, is

Answer : B

Question. A skier starts at the top of a snowball with negligible speed and skies straight down the side. At what point does he lose contact with the snow-ball?
a. θ = sin^-1( 2/3)
b. θ = cos^-1 (2/3)
c. θ = tan^-1 (2/3)
d. none of these
Answer : B

Integer

Question. A bullet fired into a fixed target loses half of its velocity after penetrating through 3cm. How much further will it penetrate before coming to rest, assuming that it faces constant resistance to motion?
Answer : 1

Question. A force of 0.5 N is applied on upper block as shown in Fig. The work done by upper block on lower block for a displacement of 3 m is:

Answer : 1

Question. A particle moves with a velocity of (2iˆ − 3 ˆj + kˆ) under the influence of a constant force F(5iˆ + 2 ˆj − 2kˆ)N.
The instantaneous power applied to the particle is:
Answer : 3

Question. The potential energy of a 2 kg particle free to move along the x-axis is given by V (x) = [x⁴/4 - x²/2] Joule
The total mechanical energy of the particle is 0.75 J. The maximum speed of the particle is:
Answer : 1

Question. A long spring, when stretched by x cm has a potential energy u. On increasing the length of spring by stretching it to 3 x cm, the potential energy stored will be n times, where n is:
Answer : 9

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