Kinematics PYQs Set 14 (PDF)

Set 14 of 14 · Questions 391-405 of 405

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Mere Teacher · Previous Year Questions JEE Main Physics · Kinematics · Set 14 (Q391-405)
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391. $A vehicle travels 4 km with speed of 3 km/h and another 4 km with speed of 5 km/h, then its average speed is :$ (1) $4.25 km/h$ (2) $3.50 km/h$ (3) $4.00 km/h$ (4) $3.75 km/h$ 392. $The initial speed of a projectile fired from ground is u. At the highest point during its motion, the speed of projectile is \frac{3}{2} u . The time of flight of the projectile is:$ (1) $\frac{u}{2 g}$ (2) $\frac{u}{g}$ (3) $\frac{2 u}{g}$ (4) $\frac{3 u}{g}$ 393. $A passenger train of length 60 m travels at a speed of 80 km / hr . Another freight train of length 120 m travels at a speed of 30 km / h . The ratio of times taken by the passenger train to completely cross the freight train when: (i) they are moving in same direction, and (ii) in the opposite directions is:$ (1) $\frac{11}{5}$ (2) $\frac{5}{2}$ (3) $\frac{3}{2}$ (4) $\frac{25}{11}$ 394. $The relation between time t and distance x of a particle is t = a x^{2} + bx, where a and b are constants. If v is the velocity of the particle, then its acceleration is$ (1) $- 2 ab v^{2}$ (2) $2 b v^{3}$ (3) $- 2 a v^{3}$ (4) $2 a v^{2}$ 395. $A particle is moving with speed v = b x along positive x -axis. Calculate the speed of the particle at time t = τ (assume that the particle is at origin at t = 0).$ (1) $\frac{b ^{2} τ}{4}$ (2) $\frac{b ^{2} τ}{2}$ (3) $b^{2} τ$ (4) $\frac{b ^{2} τ}{2}$ 396. $A train is moving slowly on a straight track with a constant speed of 2 m s^{- 1} . A passenger in that train starts walking at a steady speed of 2 m s^{- 1} to the back of the train in the opposite direction of the motion of the train. So to an observer standing on the platform directly in front of that passenger, the velocity of the passenger appears to be$ (1) $4 m s^{- 1}$ (2) $2 m s^{- 1}$ (3) $2 m s^{- 1} in the opposite direction of the train$ (4) $zero$ 397. $A helicopter is flying horizontally with a speed 'v at an altitude 'h' has to drop a food packet for man on the ground. What is the distance o helicopter from the man when the food packet is dropped?$ (1) $\frac{2 g h v ^{2} + 1}{h ^{2}}$ (2) $2 g h v^{2} + h^{2}$ (3) $\frac{2 v ^{2} h}{g} + h^{2}$ (4) $\frac{2 g h}{v ^{2}} + h^{2}$ 398. $A stone is projected at angle 30° to the horizontal The ratio of kinetic energy of the stone at point of projection to its kinetic energy at the highest point of flight will be :$ (1) $1:2$ (2) $1:4$ (3) $4 : 1$ (4) $4 : 3$ 399. $The velocity of a projectile at the initial point A is (2 i + 3 j) m/s. It’s velocity (in m/s) at point B is :$ (1) $- 2 i + 3 j$ (2) $2 i - 3 j$ (3) $2 i + 3 j$ (4) $- 2 i - 3 j$ 400. $A child stands on the edge of the cliff 10 m above the ground and throws a stone horizontally with an initial speed of 5 m s^{- 1} . Neglecting the air resistance, the speed with which the stone hits the ground will be_____m s^{- 1} (given, g = 10 m s^{- 2}).$ (1) $20$ (2) $15$ (3) $30$ (4) $25$ 401. $A body of mass 10 kg is projected at an angle of 45° with the horizontal. The trajectory of the body is observed to pass through a point (20, 10). If T is the time of flight, then its momentum vector, at time t = \frac{T}{2}, is_________[Take g= 10m/ s^{2}]$ (1) $100 i^+ (1002 - 200) j^$ (2) $1002 i^+ (100 - 2002) j^$ (3) $100 i^+ (100 - 2002) j^$ (4) $1002 i^+ (1002 - 200) j^$ 402. $A ball of mass 0.25 kg attached to the end of a string of length 1.96 m is moving in a horizontal circle. The string will break if the tension is more than 25 N. What is the maximum speed with which the ball can be moved?$ (1) $5 m / s$ (2) $3 m / s$ (3) $14 m / s$ (4) $3.92 m / s$ 403. $A girl standing on road holds her umbrella at 4 5^{\circ} with the vertical to keep the rain away. If she starts running without umbrella with a speed of 152 km h^{- 1}, the rain drops hit her head vertically. The speed of rain drops with respect to the moving girl is :$ (1) $30 km h^{- 1}$ (2) $\frac{25}{2} km h^{- 1}$ (3) $\frac{30}{2} km h^{- 1}$ (4) $25 km h^{- 1}$ 404. $If the velocity of a body related to displacement x is given v = 5000 + 24 x m / s, then the acceleration of the body is \dots.. m / s^{2}$ 405. $A tennis ball is dropped on to the floor from a height of 9.8 m. It rebounds to a height 5.0 m. Ball comes in contact with the floor for 0.2s. The average acceleration during contact is____m s^{- 2} . [Given g =10 m s^{- 2}]$