A bullet fired into a fixed target loss half of its velocity after penetrating 3cm. How much further will it penetrate before coming to rest assuming that it faces constant resistance in motion?
A.
2cm
B.
3cm
C.
1cm
D.
1.5cm
Answer: Option C
Explanation:
If u is initial velocity then v=u/2 s=3cm As v2 -u2=2as a = -u2 /8 Now v=0 Initial velocity=u/2 s=1cm Thus the bullet will penetrate a further distance of 1cm before coming to rest
From a building 2 balls A and B are thrown such that A is thrown upward and B is thrown downward. If vA and vB are their respective velocities on reaching the ground, then
A.
vB is greater than vA
B.
vB = vA
C.
vB is lesser than vA
D.
Their velocities depend on their masses.
Answer: Option B
Explanation:
Suppose the ball A is thrown upward with velocity u and ball B is thrown downward with same velocity u. After reaching the highest point the ball A comes back to its position with the same velocity in downward direction. As the 2 balls fall from the same position with the same velocity, both attain the same velocity on reaching the ground.
