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Q1. Why does the direction of motion of a projectile become horizontal at the highest point of its trajectory?

Solution

It happens so because; at highest point vertical component of velocity becomes zero.

Q2. What do you mean by a projectile?

Solution

Projectile is the name given to a body which is thrown with some initial velocity and which then move under the effect of gravity alone.

Q3. Define trajectory of a projectile.

Solution

The path followed by a projectile is known as trajectory of that projectile.

Q4. A jet airplane traveling at the speed of 500 km/hr ejects its products of combustion at the speed of 1500 km/hr relative to the jet plane. What is the speed of the later with respect to an obserever on the ground? 

Solution

Let V_g be the velocity of ejecting gases with respect to ground. velocity of jet plane  V_j = + 500 km/hr Velocity of ejected products w.r.t. jet plane  V_gj = V_g - V_j or,  V_g = V_gj   + V_j             = -1500 + 500 = -1000 km/hr    

Q5. Two trains are moving in the opposite directions on parallel tracks, one with a velocity twice that of other. If the total length of the two trains is 480 ft and they take 3 seconds to cross each other, find their individual velocities.

Solution

Let the two trains A and B be moving in opposite directions with with velocities u ans 2u respectively. Relative velocity V = u + 2u = 3u Total distance moved = total length of the two trains S = 480 ft. time taken by the trains to cross each other t = 3 seconds Now, S = Vt or, 480 = 3u x 3 or, u = 53.33 ft/s and 2u = 106.66 ft/s