Work, Energy & Power PYQs Set 9 (PDF)

Set 9 of 9 · Questions 241-248 of 248

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Mere Teacher · Previous Year Questions NEET Physics · Work, Energy & Power · Set 9 (Q241-248)
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241. $Sand is being dropped from a stationary dropper at a rate of 0.5 k g s^{- 1} on a conveyor belt moving with a velocity of 5 m s^{- 1} . The power needed to keep belt moving with the same velocity will be:$ (1) $1.25W$ (2) $2.5W$ (3) $6.25 W$ (4) $12.5 W$ 242. $A block (b) is attached to two unstretched springs S1 and S2 with spring constants k and 4 k, respectively (see figure I). The other ends are attached to identical supports M1 and M2 not attached to the walls. The springs and supports have negligible mass. There is no friction anywhere. The block B is displaced towards wall 1 by a small distance x (figure II) and released. The block returns and moves a maximum distance y towards wall 2. Displacements x and y are measured with respect to the equilibrium position of the block B. The ratio \frac{y}{x} Figure:$ (1) $4$ (2) $2$ (3) $\frac{1}{2}$ (4) $\frac{1}{4}$ 243. $A shell, in flight, explodes into four unequal parts. Which of the following is conserved?$ (1) $Potential energy$ (2) $Momentum$ (3) $Kinetic energy$ (4) $Both (a) and (c).$ 244. $What is the minimum velocity with which a body of mass m must enter a vertical loop of radius R so that it can complete the loop? (NEET‐I2016)$ (1) $3 gR$ (2) $5 gR$ (3) $gR$ (4) $2 gR$ 245. $An artillery piece of mass M_{1} fires a shell of mass M_{2} horizontally. Instantaneously after the firing, the ratio of kinetic energy of the artillery and that of the shell is :$ (1) $M_{1} / (M_{1} + M_{2})$ (2) $\frac{M _{2}}{M _{1}}$ (3) $M_{2} / (M_{1} + M_{2})$ (4) $\frac{M _{1}}{M _{2}}$ 246. $From a fixed support, two small identical spheres are suspended by means of strings of length 1 m each. They are pulled aside as shown and then released. B is the mean position. Then the two spheres collide,$ (1) $at B after 0.25 second$ (2) $at B after 0.5 second$ (3) $none of the above$ (4) $on the right side of B when the strings are inclined at 15^{\circ} with B.$ 247. $Identify the correct statements from the following: (A) Work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket is negative. (B) Work done by gravitational force in lifting a bucket out of a well by a rope tied to the bucket is negative. (C) Work done by friction on a body sliding down an inclined plane is positive, (D) Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity in zero. (E) Work done by the air resistance on an oscillating pendulum in negative. Choose the correct answer from the options given below:$ (1) $B and E only$ (2) $A and C only$ (3) $B, D and E only$ (4) $B and D only$ 248. $A stone tide to a string of length L is whirled in a vertical circle with the other end of the string at the center. At a certain instant of time, the stone is at its lowest position and has a speed u. The magnitude of change in its velocity, as it reaches a position where the string is horizontal, is x (u^{2} - g L) .The value of x is$ (1) $3$ (2) $2$ (3) $1$ (4) $5$