Newton's Laws of Motion PYQs Set 5 (PDF)

Set 5 of 7 · Questions 121-150 of 197

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Mere Teacher · Previous Year Questions JEE Main Physics · Newton's Laws of Motion · Set 5 (Q121-150)
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121. $The X and Y components of a force F acting at 30^{\circ} to x-axis are respectively$ (1) $\frac{F}{2}, F$ (2) $\frac{F}{2}, \frac{3}{2} F$ (3) $\frac{3}{2} F, \frac{1}{2} F$ (4) $F, \frac{F}{2}$ 122. $One end of the string of length l is connected to a particle of mass m and the other end is connected to a small peg on a smooth horizontal table. If the particle moves in circle with speed v, the net force on the particle (directed towards centre) will be (T represents the tension in the string) [NEET 2017]$ (1) $T$ (2) $T + \frac{m v ^{2}}{l}$ (3) $T - \frac{m v ^{2}}{l}$ (4) $zero$ 123. $An infinite number of masses are placed on a frictionless table and they are connected via massless strings. Their masses follow the sequence, m, \frac{m}{2}, \frac{m}{6}, \dots \dots \dots \frac{m}{n !}, \dots \dots . . and they are further connected to a mass m that hangs over a massless pulley. The acceleration of the hanging mass is$ (1) $\frac{g}{e - 1}$ (2) $\frac{g}{e + 1}$ (3) $\frac{g}{e}$ (4) $\frac{g}{2 e}$ 124. $Two bodies of mass 4 kg and 6 kg are tied to the ends of a massless string. The string passes over a pulley which is frictionless (see figure). The acceleration of the system in terms of acceleration due to gravity g is [NEET 2020]$ (1) $9/2$ (2) $g /5$ (3) $g /10$ (4) $g$ 125. $Two blocks A and B of masses 3 m and m, respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the string is cut, are respectively [NEET2017]$ (1) $g, \frac{g}{3}$ (2) $\frac{g}{3}, g$ (3) $g, g$ (4) $\frac{g}{3}, \frac{g}{3}$ 126. $Two stones of masses m and 2m are whirled in horizontal circles, the heavier one in a radius r /2 and the lighter one in radius r. The tangential speed of lighter stone is n times that of the value of heavier stone when they experience same centripetal forces. The value of n is$ (1) $4$ (2) $1$ (3) $2$ (4) $3$ 127. $The position-time (x - t) graph of a moving body of mass 2 kg is shown in the figure. The impulse on the body at t = 4 s is$ (1) $1.5 kg - ms^{- 1}$ (2) $- 1.5 kg - ms^{- 1}$ (3) $1 kg - ms^{- 1}$ (4) $2 kg - ms^{- 1}$ 128. $A small ball of mass m is thrown upward with velocity u from the ground. The ball experiences a resistive force mkv^{2}, where V is its speed. The maximum height attained by the ball is$ (1) $\frac{1}{2 k} tan^{- 1} \frac{k u ^{2}}{g}$ (2) $\frac{1}{k} In (1 + \frac{k u ^{2}}{2 g})$ (3) $\frac{1}{2 k} In (1 + \frac{k u ^{2}}{g})$ (4) $\frac{1}{k} tan^{- 1} \frac{ku ^{2}}{2 g}$ 129. $A man of mass m stands on a crate of mass M. He pulls on a light rope passing over a smooth light pulley. The other end of the rope is attached to the crate. For the system to be in equilibrium, the force exerted by the men on the rope will be$ (1) $(M + m) g$ (2) $\frac{1}{2} (M + m) g$ (3) $Mg$ (4) $mg$ 130. $A monkey of mass 20 kg is holding a vertical rope. The rope will not break when a mass of 25 kg is suspended from it but will break if the mass exceeds 25 kg. What is the maximum acceleration with which the monkey can climb up along the rope7. (g = 10 m / s^{2})$ (1) $5 m / s^{2}$ (2) $10 m / s^{2}$ (3) $25 m / s^{2}$ (4) $2.5 m / s^{2}$ 131. $In two different experiments, an object of mass 5 kg moving with a speed of 25 m s^{- 1} hits two different walls and comes to rest within (i) 3 second, (ii) 5 seconds, respectively. Choose the correct option out of the following:$ (1) $Impulse and average force acting on the object will be same for both the cases.$ (2) $Impulse will be same for both the cases but the average force will be different.$ (3) $Average force will be same for both the cases but the impulse will be different.$ (4) $Average force and impulse will be different for both the cases.$ 132. $The boxes of masses 2kg and 8kg are connected by a massless string passing over smooth pulleys. Calculate the time taken by box of mass 8kg to strike the ground starting from rest. (use g=10 m/ s^{2})$ (1) $0.34s$ (2) $0.2s$ (3) $0.25s$ (4) $0.4s$ 133. $The force F acting on a particle of mass m is indicated by the force‐time graph as shown. The change in momentum of the particle over the time interval from zero to 8 s is$ (1) $24 Ns$ (2) $20 Ns$ (3) $12 Ns$ (4) $6 Ns$ 134. $A particle moving with velocity v is acted by three forces shown by the vector triangle PQR . The velocity of the particle will [NEET 2019]$ (1) $decrease$ (2) $remain constant$ (3) $change according to the smallest force QR$ (4) $increase$ 135. $A block of mass 8 kg is suspended by a rope of length 3 m from the ceiling. A force of 40 N is applied horizontally to the block. Then the angle that the rope makes with the vertical in equilibrium is (acceleration due to gravity = 10 m s^{- 2}, neglect the mass of the rope)$ (1) $sin^{- 1} (\frac{1}{2})$ (2) $tan^{- 1} (\frac{1}{2})$ (3) $sin^{- 1} (\frac{1}{3})$ (4) $tan^{- 1} (\frac{1}{3})$ 136. $The normal reaction 'N' for a vehicle of 800kg mass, negotiating a turn on a 3 0^{0} banked road at maximum possible speed without skidding is ___x 1 0^{3} kgm/ s^{2} .$ (1) $10.2$ (2) $7.2$ (3) $12.4$ (4) $6.96$ 137. $A bullet of '4g' mass is fired from a gun of mass 4kg. If the bullet moves with the muzzle speed of 50 m s^{- 1}, the impulse imparted to the gun and velocity of recoil of gun are:$ (1) $0.4 kg m s^{- 1}, 0.1 m s^{- 1}$ (2) $0.2 kg m s^{- 1}, 0.05 m s^{- 1}$ (3) $0.2 kg m s^{- 1}, 0.1 m s^{- 1}$ (4) $0.4 kg m s^{- 1}, 0.05 m s^{- 1}$ 138. $A particle of mass m is suspended from a ceiling through a string of length L . If the particle moves in a horizontal circle of radius r as shown in the figure, then the speed of the particle is$ (1) $r \frac{g}{L ^{2} - r ^{2}}$ (2) $g \frac{r}{L ^{2} - r ^{2}}$ (3) $2rgL2-r2$ (4) $2grL2-r2$ 139. $A bomb at rest explodes into 3 parts of same mass. The momentum of two parts is - 3 p i and 2 p j respectively. The magnitude of momentum of third part is$ (1) $p$ (2) $5 p$ (3) $11 p$ (4) $13 p$ 140. $Given below are two statements: Statement-I: An elevator can go up or down with uniform speed when its weight is balanced with the tension of its cable. Statement-II: Force exerted by the floor of an elevator on the foot of a person standing on it is more than his/her weight when the elevator goes down with increasing speed. In the light of the above statements, choose the correct answer from the options given below:$ (1) $Both statement 1 and statement II are false$ (2) $Statement I is true but Statement II is false$ (3) $Both Statement I and Statement II are true$ (4) $Statement I is false but Statement II is true$ 141. $Sum of magnitude of two forces is 25 N . The resultant of these forces is normal to the smaller force and has a magnitude of 10 N . Then the two forces are$ (1) $14.5 N, 10.5 N$ (2) $16 N, 9 N$ (3) $13 N, 12 N$ (4) $20 N, 5 N$ 142. $Two masses m_{1} and m_{2} are placed on a smooth horizontal surface and are connected by a string of negligible mass. A horizontal force F is applied on the mass m_{2} as shown in the figure. The tension in the string is$ (1) $(\frac{m _{1}}{m _{1} + m _{2}}) F$ (2) $\frac{m _{2} F}{m _{1} + m _{2}}$ (3) $(\frac{m _{1}}{m _{2}}) F$ (4) $\frac{m _{2} F}{m _{1}}$ 143. $The maximum acceleration with which a body of mass 200 kg is lowered into a well using a rope having a breaking force of 50 kg -wt is (Acceleration due to gravity = 10 ms^{- 2})$ (1) $7.5 ms^{- 2}$ (2) $5 ms^{- 2}$ (3) $3 ms^{- 2}$ (4) $2.5 ms^{- 2}$ 144. $In a rocket, fuel burns at the rate of 1 kg/s This fuel is ejected from the rocket with a velocity of 60 km/s. This exerts a force on the rocket equal to$ (1) $6000 N$ (2) $60000 N$ (3) $60 N$ (4) $600 N$ 145. $A block is between two surfaces as shown in the figure. Find the normal reaction at both surfaces. [Assume, g = 10 m / s^{2}]$ (1) $N_{1} = 37.2 N and N_{2} = 9.6 N$ (2) $N_{1} = 382 N and N_{2} = 8.6 N$ (3) $N_{1} = 40 N and N_{2} = 4 N$ (4) $N_{1} = 37.5 N and N_{2} = 9.9 N$ 146. $A man fires a bullet of mass 200 g at a speed of 5 m/s. Ke gun is of one kg mass. By what velocity the gun rebounds backward?.$ (1) $1 m/s$ (2) $0.01 m/s$ (3) $0.1 m/s$ (4) $10 m/s.$ 147. $A 0.5 k g ball moving with a speed of 12m/s strikes a hard wall at an angle of 3 0^{o} with the wall. It is reflected with the same speed at the same angle. If the ball is in contact with the wall for 0.25 seconds, the average force acting on the wall is$ (1) $96 N$ (2) $48 N$ (3) $24 N$ (4) $12 N.$ 148. $In the following figure the masses of the blocks A and B are same and each equal to m. The tensions in the strings OA and AB are T_{2} and T_{1} respectively. The system is in equilibrium with a constant horizontal force mg on B. The T_{1} is$ (1) $mg$ (2) $2 m g$ (3) $3 m g$ (4) $5 m g$ 149. $250 N force is required to raise 75 kg mass from a pulley If rope is pulled 12 m then the load is lifted to 3 m, the efficiency of pulley system will be$ (1) $25%$ (2) $33.3%$ (3) $75%$ (4) $90%.$ 150. $If W_{1}, W_{2} and W_{3} represent the work done in moving a particle from A to B along three different paths 1,2 and 3 (as shown in figure) in the gravitational field of the point mass ' m'. Find the correct relation between ' W_{1}, ' W_{2}' and ' W_{3}'$ (1) $W_{1} < W_{3} < W_{2}$ (2) $W_{1} < W_{2} < W_{3}$ (3) $W_{1} = W_{2} = W_{3}$ (4) $W_{1} > W_{3} > W_{2}$