Work, Energy & Power PYQs Set 7 (PDF)

Set 7 of 9 · Questions 181-210 of 248

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Mere Teacher · Previous Year Questions NEET Physics · Work, Energy & Power · Set 7 (Q181-210)
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181. $A mass of 1 kg falls from a height of 1 m and lands on a mass less platform supported by a spring having spring constant 15 Nm^{- 1} as shown in the figure. The maximum compression of the spring is. (acceleration due to gravity = 10 ms^{- 2})$ (1) $2 m$ (2) $2 m$ (3) $(\frac{2}{3}) m$ (4) $3 m$ 182. $In case of vertical circular motion of a particle by a thread of length r if the tension in the thread is zero at an angle 30^{\circ} shown in figure, the velocity at the bottom point (A) of the circular path is (g = gravitational acceleration)$ (1) $\frac{7}{2} gr$ (2) $5 gr$ (3) $4 gr$ (4) $\frac{5}{2} gr$ 183. $Consider a force F = - x i^+ y j^. The work done by this force in moving a particle from point A(1, 0) to B(0, 1) along the line segment is: (All quantities are in SI units)$ (1) $\frac{1}{2}$ (2) $\frac{3}{2}$ (3) $2$ (4) $1$ 184. $A body of mass ' m' connected to a massless and unstretchable string goes in verticle circle of radius ' R'under gravity g . The other end of the string is fixed at the center of circle. If velocity at top of circular path is n gR, where, n ⩾ 1, then ratio of kinetic energy of the body at bottom to that at top of the circle is$ (1) $\frac{n ^{2}}{n ^{2} + 4}$ (2) $\frac{n ^{2} + 4}{n ^{2}}$ (3) $\frac{n + 4}{n}$ (4) $\frac{n}{n + 4}$ 185. $A particles of mass m_{1} moving along the X -axis collides with a stationary particle of mass m_{2} and deviates by an angle 30^{\circ} to the X -axis as shown in the figure. If the percentage change in kinetic energy of the combined system of there two particles reduces by 50 %, then the ratio of the masses \frac{m _{2}}{m _{1}} is$ (1) $8$ (2) $6$ (3) $\frac{8}{7}$ (4) $\frac{1}{6}$ 186. $A block of mass 10 kg, moving in x direction with a constant speed of 10 m s^{- 1}, is subject to a retarding force F = 0.1 x J/m during its travel from x = 20 m to 30 m. Its final KE will be:$ (1) $450 J$ (2) $275 J$ (3) $250 J$ (4) $475 J$ 187. $Given below is the plot of a potential energy function U(x) for a system, in which a particle is in one dimensional motion, while a conservative force F(x) acts on it. Suppose that E_{m ec h} =8J, the incorrect statement for this system is:$ (1) $at x> x_{4}, K.E. is constant throughout the region.$ (2) $at x< x_{1}, K.E. is smallest and the particle is moving at the slowest speed.$ (3) $at x= x_{2}, K.E is greatest and the particle is moving at the fastest speed.$ (4) $at x= x_{3}, K.E.=4J$ 188. $A body of mass 0.5 kg travels on straight line path with velocity v = (3 x^{2} +4) m/s. The net work done by the force during its displacement from x = 0 to x = 2 m is:$ (1) $64 J$ (2) $60 J$ (3) $120 J$ (4) $128 J$ 189. $An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are, 1 kg first part moving with a velocity of 12 m s^{- 1} and 2 kg second part moving with a velocity 8 m s^{- 1} . If the third part flies off with a velocity of 4 m s^{- 1}, its mass would b$ (1) $7 kg$ (2) $17 kg$ (3) $3 kg$ (4) $5 kg$ 190. $A particle moves in one dimension from rest under the influence of a force that varies with the distance travelled by the particle as shown in the figure. The kinetic energy of the particle after it has travelled 3m is:$ (1) $4 J$ (2) $2.5 J$ (3) $6.5 J$ (4) $5 J$ 191. $A time dependent force F = 6t acts on a particle of mass 1kg. If the particle starts from rest, the work done by the force during the first 1 sec. will be:$ (1) $18 J$ (2) $4.5 J$ (3) $22 J$ (4) $9 J$ 192. $A body of mass 'm' dropped from a height 'h' reaches the ground with a speed of 0.8 g h . The value of work done by the air-friction is:$ (1) $-0.68mgh$ (2) $mgh$ (3) $1.64mgh$ (4) $0.64mgh$ 193. $An object of mass 500 g, initially at rest, is acted upon by a variable force whose X-component varies with X in the manner shown. The velocities of the object at the points X = 8 m and X = 12 m, would have the respective values of (nearly)$ (1) $18 m/s and 24.4 m/s$ (2) $23 m/s and 24.4 m/s$ (3) $23 m/s and 20.6 m/s$ (4) $18 m/s and 20.6 m/s$ 194. $A body of mass (4 m) is lying in x‐y plane at rest. It suddenly explodes into three pieces. Two pieces, each of mass (m) move perpendicular to each other with equal speeds (v). The total kinetic energy generated due to explosion is$ (1) $m v^{2}$ (2) $\frac{3}{2} m v^{2}$ (3) $2 m v^{2}$ (4) $4 m v^{2}$ 195. $A particle moves from a point (-2 i^+ 5 j^) to (4 j^+ 3 k^) when a force of (4 i^+ 3 j^) N is applied. How much work has been done by the force$ (1) $2J$ (2) $8 J$ (3) $11 J$ (4) $5 J$ 196. $A ball of mass 0.5 kg moving horizontally at 10 ms^{- 1} strikes a vertical wall and rebounds with speed V . The magnitude of the change in linear momentum is found to be 8.0 kgms^{- 1} . The magnitude of V is$ (1) $6.0 ms^{- 1}$ (2) $9.0 ms^{- 1}$ (3) $26.0 ms^{- 1}$ (4) $13.0 ms^{- 1}$ 197. $The ratio of powers of two motors is \frac{3 x}{x + 1}, that are capable of raising 300 kg water in 5 minutes and 50 kg water in 2 minutes respectively from a well of 100 m deep. The value of x will be$ (1) $16$ (2) $2$ (3) $2.4$ (4) $4$ 198. $A point mass m is moved in a vertical circle of radius r with the help of a string. The velocity of the mass is 7 gr at the lowest point. The tension in the string at the lowest point is [NEET 2020]$ (1) $6 mg$ (2) $7 mg$ (3) $8 mg$ (4) $1 mg$ 199. $The bob of a pendulum was released from a horizontal position. The length of the pendulum is 10 m . If it dissipates 10 % of its initial energy against air resistance, the speed with which the bob arrives at the lowest point is : [Use, g : 10 ms^{- 2}]$ (1) $65 ms^{- 1}$ (2) $56 ms^{- 1}$ (3) $55 ms^{- 1}$ (4) $25 ms^{- 1}$ 200. $A body of m kg slides from rest along the curve of vertical circle from point A to B in friction less path. The velocity of the body at B is: (given, R = 14 m, g = 10 m / s^{2} and 2 = 1.4)$ (1) $16.7 m / s$ (2) $19.8 m / s$ (3) $10.6 m / s$ (4) $21.9 m / s$ 201. $A time varying force acts on a ball of mass 100 g for 2 ms . The force versus time curve is shown below. If the initial speed of the ball is 10 m / s, then the speed of ball after 2 ms is$ (1) $210 m / s$ (2) $410 m / s$ (3) $200 m / s$ (4) $400 m / s$ 202. $The work done by a force acting on a body is as shown in the graph. The total work done in covering an initial distance of 20 m is$ (1) $225 J$ (2) $200 J$ (3) $400 J$ (4) $175 J$ 203. $A particle is moving in a circular path of radius a under the action of an attractive potential U = - \frac{k}{2 r ^{2}} . Its total energy is:$ (1) $zero$ (2) $- \frac{3}{2} \frac{k}{a ^{2}}$ (3) $- \frac{k}{4 a ^{2}}$ (4) $\frac{k}{2 a ^{2}}$ 204. $In the given figure, the block of mass m is dropped from the point 'A'. The expression for kinetic energy of block when it reaches point 'B' is:$ (1) $\frac{1}{2} mg y_{0}^{2}$ (2) $\frac{1}{2} mg y^{2}$ (3) $mg (y - y_{0})$ (4) $m g y_{0}$ 205. $Force F on a particle moving in a straight line varies with distance d as shown in figure. The work done on the particle during its displacement of 12 m is$ (1) $18 J$ (2) $21 J$ (3) $26 J$ (4) $13 J$ 206. $A block of mass m is kept on a platform which starts from rest with constant acceleration g/2 upward, as shown in figure. Work done by normal reaction on block in time t is:$ (1) $\frac{m g ^{2} t ^{2}}{8}$ (2) $0$ (3) $- \frac{m g ^{2} t ^{2}}{8}$ (4) $\frac{3 m g ^{2} t ^{2}}{8}$ 207. $A particle of mass 500 gm is moving in a straight line with velocity u = b x^{5/2} . The work done by the net force during its displacement from x = 0 to x = 4 mis: (Take b = 0.25 m^{- 3/2} s^{- 1}).$ (1) $2J$ (2) $4J$ (3) $8 J$ (4) $16 J$ 208. $A body initially at rest and sliding along a frictionless track from a height h (as shown in the figure) just completes a vertical circle of diameter AB = D . The height h is equal to (NEET2018)$ (1) $\frac{3}{2} D$ (2) $D$ (3) $\frac{7}{5} D$ (4) $\frac{5}{4} D$ 209. $Particle moves from point A to point B along the line shown in figure under the action of force. F \to= - x i^+ y j^. Determine the work done on the particle by F \to in moving the particle from point A to point B$ (1) $1J$ (2) $\frac{1}{2} J$ (3) $2J$ (4) $3J$ 210. $On a frictionless surface, a block of mass M moving at speed v collides elastically with another block of same mass M which is initially at rest. After collision the first block moves at an angle 6 to its initial direction and has a speed \frac{v}{3} . The second block’s speed after the collision is$ (1) $\frac{3}{2} v$ (2) $\frac{3}{2} v$ (3) $\frac{2 2}{3} v$ (4) $\frac{3}{4} v$