EASY
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The kinetic energy of a projectile at the highest point is half of the initial kinetic energy. The angle of projection with the horizontal is

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Important Questions on Motion in a Plane

MEDIUM
The position of a projectile launched from the origin at t = 0 is given by r = 4 i ^ + 5 j ^ m   at t = 2s. If the projectile was launched at an angle θ  from the horizontal, then θ   is (take g = 10 ms-2).
EASY
A projectile is given an initial velocity of i^+2j^ m s-1, where i ^ is along the ground and j ^ is along the vertically upward direction. If g=10 m s-2, the equation of its trajectory is :
EASY
A boy is standing on top of a tower of height, 85 m and throws a ball in the vertically upward direction with a certain speed. If 5.25 s later he hears the ball hitting the ground, then the speed with which the boy threw the ball is (take g=10 m s-2, the speed of sound in air is 340 m s-1)
MEDIUM
A projectile is fired from the surface of the earth with a velocity of 5 m s-1 and angle θ with the horizontal. Another projectile fired from another planet with a velocity of 3 m s-1 at the same angle follows a trajectory which is identical with the trajectory of the projectile fired from the earth. The value of the acceleration due to gravity on the planet is: (given =9.8 m s-2)
EASY

The velocity of a projectile at the initial point A is 2i^-3j^ m s-1. Its velocity (in m s-1) at point B is

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HARD
A ball is thrown from ground at an angle θ with horizontal and with an initial speed u0. For the resulting projectile motion, the magnitude of average velocity of the ball up to the point when it hits the ground for the first time is V1. After hitting the ground, ball rebounds at the same angle θ but with a reduced speed of u0α. Its motion continues for a long time as shown in figure. If the magnitude of average velocity of the ball for entire duration of motion is 0.8V1, the value of α is______

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HARD
A small boy is throwing a ball towards a wall 6 m in front of him. He releases the ball at a height of 1.4 m from the ground. The ball bounces from the wall at a height of 3 m, rebounds from the ground and reaches the boy's hand exactly at the point of release. Assuming the two bounces (one from the wall and the other from the ground) to be perfectly elastic, how far ahead of the boy did the ball bounce from the ground?
EASY
At what angle θ to the horizontal should an object is projected so that the maximum height reached is equal to the horizontal range?
HARD

Two particles are simultaneously projected in the horizontal direction from a point P at a certain height. The initial velocities of the particles are oppositely directed to each other and have magnitude v each. The separation between the particles at a time when their position vectors (drawn from the point P) are mutually perpendicular, is:

HARD
A mobile phone of mass 100 g falls from the hand of a person through the window of a train. The train is accelerating at 1 m s-2 and just 20 s have passed since it left the station from standstill. If the window is 2 m above the ground. With what kinetic energy will the phone will hit the ground? g=10 m s-2
HARD
A plane is inclined at an angle α=30° with respect to the horizontal. A particle is projected with a speed  u=2 m s-1 , from the base of the plane, making an angle θ=15° with respect to the plane as shown in the figure. The distance from the base, at which the particle hits the plane is close to:
(Take  g=10 m s-2 )
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EASY
Two bodies are projected at angles θ and 90o-θ to the horizontal with the same speed. The ratio of their times of flight is
MEDIUM
Two particles are projected from the same point with the same speed u such that they have the same range R, but different maximum heights, h1 and h2. Which of the following is correct?
MEDIUM
When an object is shot from the bottom of a long smooth inclined plane kept at an angle 60° with horizontal, it can travel a distance x1 along the plane. But, when the inclination is decreased to 30° and the same object is shot with the same velocity, it can travel x2 distance. Then x1:x2 will be
MEDIUM
A shell is fired from a fixed artillery gun with an initial speed u such that it hits the target on the ground at a distance R from it. If t1 and t2 are the values of the time taken by it to hit the target in two possible ways, the product t1t2 is:
MEDIUM
A projectile is given an initial velocity of i^+3 j^ m s-1, where i^ is along the ground and j^ is along the vertical. Then, the equation of the path of projectile is [Take, g=10 m s-2
HARD
The horizontal range and maximum height attained by a projectile are R and H respectively. If a constant horizontal acceleration a=g4 is imparted to the projectile due to wind, then its horizontal range and maximum height will be 
EASY
Two guns A and B can fire bullets at speeds 1 km s-1 and 2 km s-1 respectively. From a point on a horizontal ground, they are fired in all possible directions. The ratio of maximum areas covered by the bullets fired by the two guns, on the ground is:
MEDIUM
Two balls are projected at an angle θ and (90°-θ) with respect to the horizontal with the same speed. The ratio of their maximum vertical heights is
HARD
A ball is projected from the ground at an angle of 45° with the horizontal surface. It reaches a maximum height of 120 m and returns to the ground. Upon hitting the ground for the first time, it loses half of its kinetic energy. Immediately after the bounce, the velocity of the ball makes an angle of 30° with the horizontal surface. The maximum height it reaches after the bounce (in meters) is _____________.