Question

In the figure shown the velocity of lift is 2 m/s while string
is winding on the motor shaft with velocity 2 m/s and block
A is moving downwards with a velocity of 2 m/s, then find
out the velocity of block B.
(A) 2 m/s upward
(B) 2 m/s downward
(C) 4 m/s (D) 8 m/s ​

Answer 1

Answer:

The answer is not present in the option.

Explanation:

According to the figure,

The velocity of lift is 2 m/s while string

is winding on the motor shaft with velocity 2 m/s and block

A is moving downwards with a velocity of 2 m/s,

Let the length of the string is l

Velocity of the lift, = 2m/s

Velocity of the string = 2 m/s

                                       = -dl/dt = 2m /s

Now according to the problem the velocity of the box A= 2 m/s

From the constraint

s= u-(l-u)

s= 2u-l

differentiate both side with respect to time t

ds/dt= 2du/dt-dl/dt

        = 2(2)-  (-2)

        = 4+2

         = 6

Answer 2

Answer:answer is 8m/s

Explanation: