12
A projectile is launched at 45° to the horizontal with initial K.E., E. Assuming air resistance to be negligible, what will be the kinetic energy of the projectile when it reaches its highest point?
Correct Answer:B
Explanation:
At the highest point, only the horizontal component of velocity remains, which is v0 cos 45° = v0/√2. Thus, KE = 0.5m(v0/√2)² = 0.5E.
13
When a heavy coin falls a short distance towards the ground it does not reach terminal velocity. Why is this so?
Correct Answer:D
Explanation:
Terminal velocity is not reached because the distance is too short for air resistance to balance the coin's weight.
14
Two balls collide each other, it has been observed that the collision is elastic. Which statement advocates the observation?
Correct Answer:A
Explanation:
In elastic collisions, both kinetic energy and momentum are conserved.