Question
Physics Question on Motion in a plane
A system is shown in the figure. A man standing on the block is pulling the rope. The velocity of the point of string in contact with the hand of the man is 2 m/s downwards. The velocity of the block will be [assume that the block does not rotate]
A
3 m/s
B
2 m/s
C
½ m/s
D
1 m/s
Answer
2 m/s
Explanation
Solution
The correct answer is (B): 2 m/s
Divide the total length of the rope into segments, then
l1 + l2 + l3 + l4 = constant
Differential above equation with respect to time t, we get
dl1/dt + dl2/dt + dl3/dt + dl4/dt = 0
⇒ v1 + v2 + v3 + v4 = 0
Taking the downward velocity as positive and upward velocity as negative, then
-v + v + v + 2 = 0
⇒ v = 2 m/s