Work, Energy & Power PYQs Set 4 (PDF)

Set 4 of 10 · Questions 91-120 of 294

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Mere Teacher · Previous Year Questions JEE Main Physics · Work, Energy & Power · Set 4 (Q91-120)
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91. $Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m / s . Take g constant with a value of 10 m / s^{2} . The work done by the (i) gravitational force and the (ii) resistive force of air is [NEET 2017]$ (1) $(i) -10 J, (ii) -8.25 J$ (2) $(i) 1.25 J, (ii) -8.25 J$ (3) $(i) 100 J, (ii) 8.75 J$ (4) $(i) 10 J, (ii) -8.75 J$ 92. $The work done on a particle of mass m by a force, K (\frac{x}{( x ^{2} + y ^{2} ) ^{3/2}} i + \frac{y}{( x ^{2} + y ^{2} ) ^{3/2}} j) (K being a constant of appropriate dimensions), when the particle is taken from the point (a, 0) to the point (0, a) along a circular path of radius a about the origin in the x-y plane is:$ (1) $\frac{2 Kπ}{a}$ (2) $\frac{Kπ}{a}$ (3) $\frac{Kπ}{2 a}$ (4) $0$ 93. $When a body is acted upon by a resultant force, then the work done by the resultant force is equal to$ (1) $its initial kinetic energy$ (2) $its initial potential energy$ (3) $change in the kinetic energy$ (4) $change in the potential energy$ 94. $A pump on the ground floor of a building can pump up water to. fill a tank of volume 36 m^{3} in 30 min . If the tank is 50 m above the ground, and the electric power consumed by the pump is 40 kW, the efficiency of the pump is (Use g = 10 m / s^{2} and density of water = 1000 kg / m^{3})$ (1) $30 %$ (2) $25 %$ (3) $33 %$ (4) $40 %$ 95. $A ball of mass 0.2 kg is thrown vertically upwards by applying a force by hand. If the hand moves 0.2 m while applying the force and the ball goes upto 2 m height further, find the magnitude of the force. Consider g = 10 m/ s^{2}$ (1) $22 N$ (2) $4 N$ (3) $16 N$ (4) $20 N$ 96. $When a body moves with a constant speed along a circle$ (1) $no work is done on it$ (2) $no acceleration is produced in it$ (3) $its velocity remains constant$ (4) $no force acts on it.$ 97. $A body of mass 8 kg and another of mass 2 kg are moving with equal kinetic energy. The ratio of their respective momenta will be:$ (1) $1:1$ (2) $2: l$ (3) $1:4$ (4) $4: l$ 98. $When a force F = 17 - 2 x + 6 x^{2} N acts on a body of mass 2 kg and displaces it from x = 0 m to x = 8 m, the work done is$ (1) $1096 J$ (2) $270 J$ (3) $35 J$ (4) $135 J$ 99. $Consider a rocket is being fired. The kinetic energy of the rocket is increased by 16 times whereas its total mass is reduced by half through the burning of fuel. The factor by which its momentum increases is$ (1) $8$ (2) $22$ (3) $4$ (4) $42$ 100. $An automatic gun fires 360 bullets per minute with a speed of 360 km / h . If each bullet weight 20 g, the power of the gun is$ (1) $75 W$ (2) $150 W$ (3) $300 W$ (4) $600 W$ 101. $A ball (initially at rest) is released from the top of tower. The ratio of work done by the force of gravity, in the first, second and third seconds is$ (1) $1 : 3 : 5$ (2) $1 : 4 : 16$ (3) $1 : 9 : 25$ (4) $1 : 2 : 3$ 102. $If a force F is applied on a body and it moves with a velocity v, the power will be$ (1) $F \cdot v$ (2) $\frac{F}{v}$ (3) $\frac{F}{v ^{2}}$ (4) $F \cdot v^{2}$ 103. $Which one of the following forces cannot be expressed in terms of potential energy?$ (1) $Frictional force$ (2) $Coulomb's force$ (3) $Restoring force$ (4) $Gravitational force$ 104. $A particle of mass 100 g is thrown vertically upwards with a speed of 5 m/s. the work done by the force of gravity during the time the particle goes up is$ (1) $- 0.5 J$ (2) $-1.25 J$ (3) $+1.25 J$ (4) $0.5 J$ 105. $A particle moves from a point (- 2 i + 5 j) to (4 j + 3 k) when a force of (4 i + 3 j) N is applied. How much work has been done by the force? (NEET‐II2016)$ (1) $8 J$ (2) $11 J$ (3) $5 J$ (4) $2 J$ 106. $A force F = 2 i + bj + k is applied on a particle and it undergoes a displacement i - 2 j - k . What will be the value of b, if work done on the particle is zero.$ (1) $0$ (2) $\frac{1}{2}$ (3) $2$ (4) $\frac{1}{3}$ 107. $A bullet of mass 10 g leaves a rifle at an initial velocity of 1000 m / s and strikes the earth at the same level with a velocity of 500 m / s . The work done injoule overcoming the resistance of air will be$ (1) $375$ (2) $3750$ (3) $5000$ (4) $500$ 108. $A body of mass 2 kg is moving along x -direction such that its displacement as function of time is given by x (t) = α t^{2} + βt + γm, where α = 1 m / s^{2}, β = 1 m / s and γ = 1 m . The work done on the body during the time interval t = 2 s to t = 3 s, is____J.$ (1) $12$ (2) $49$ (3) $42$ (4) $24$ 109. $300 J of work is done in sliding a 2 kg block up an inclined plane ofheight 10 m . Work done against friction is (Take g = 10 m / s^{2})$ (1) $1000 J$ (2) $200 J$ (3) $100 J$ (4) $zero.$ 110. $A spring has a spring constant 200 Nm^{- 1} . If it is stretched by 1 cm then the potential energy stored in it is$ (1) $100 J$ (2) $0.01 J$ (3) $10 J$ (4) $1 J$ 111. $Hammer of mass M strikes a nail of mass m with a velocity 20 m / s into a fixed wall. The nail penetrates into the wall to a depth of 1 cm . The average resistance of the wall to the penetration of the nail is$ (1) $(\frac{M ^{2}}{M + m}) \times 10^{3}$ (2) $\frac{2 M ^{2}}{M + m} \times 10^{4}$ (3) $\frac{M + m}{M ^{2}} \times 10^{2}$ (4) $\frac{M ^{2}}{M + m} \times 10^{2}$ 112. $A body moves a distance of 10 m along a straight line under the action of a 5 N force. If the work done is 25 J, then angle between the force and direction of motion of the body is$ (1) $6 0^{o}$ (2) $7 5^{o}$ (3) $3 0^{o}$ (4) $4 5^{o}$ 113. $A constant force of 5N Accelerates a stationary particle of mass 500 g through a displacement of 5 m . The average power delivered is$ (1) $6.25 W$ (2) $25 W$ (3) $62.5 W$ (4) $50 W$ 114. $The kinetic energy of a car is doubled when its velocity is increased by 1 ms^{- 1} . Then the initial velocity of the car is$ (1) $(2 + 2) ms^{- 1}$ (2) $(1 - 2) ms^{- 1}$ (3) $(2 - 2) ms^{- 1}$ (4) $(1 + 2) ms^{- 1}$ 115. $A particle of mass m is initially at rest at the origin. It is subjected to a force and starts moving along the x-axis. Its kinetic energy K changes with time as dK/dt = γ t where λ is a positive constant of appropriate dimensions. Which of the following statements is (are) true?$ (1) $The force applied on the particle is constant$ (2) $The speed of the particle is proportional to time$ (3) $The distance of the particle from the origin increases linearly with time$ (4) $The force is conservative$ 116. $A toy car of mass 100 g is moving with velocity of (i + 2 j - 3 k) m, then the kinetic energy of the car is$ (1) $7 J$ (2) $70 J$ (3) $0.7 J$ (4) $0.07 J$ 117. $A particle is projected making an angle of 4 5^{o} with horizontal having kinetic energy K . The kinetic energy at highest point will be$ (1) $\frac{K}{2}$ (2) $\frac{K}{2}$ (3) $2K$ (4) $K .$ 118. $There are four bulbs of power 100 W, 200 W, 500 W and 1000 W . Among these whose filament has high resistance? (Assuming, same voltage source)$ (1) $100 W bulb$ (2) $200 W bulb$ (3) $500 W bulb$ (4) $1000 W bulb$ 119. $A beam of electrons of energy E scatters from a target having atomic spacing of 1 ∖ AA A . The first maximum intensity occurs at θ = 60^{\circ} . Then E (in eV) is (Planck constant h = 6.64 \times 10^{- 34} Js, 1 eV = 1.6 \times 10^{- 19} J, electron mass m = 9.1 \times 10^{- 31} kg)$ 120. $A spherical body of mass 2 kg starting from rest acquires a kinetic energy of 10000 J at the end of 5^{t h} second. The force acted on the body is____N.$