Question

A block of mass m is pulled by an external agent by an inextensible string at point P as shown in the
figure:

my?
Kinetic energy of the block is
50
тау
25
2) power delivered by the external agent is 25
3) Total power delivered by the string is zero
4) Work done by the string on the block is non-zero
​

Answer 1

Answer:

A) Kinetic energy of the block is $K = \frac{mv^2}{50}$

B) Power delivered by external agent is $P = \frac{mav}{25}$

D) Work done by the string on the block is nonzero

Explanation:

As shown in the figure if the string is pulled at speed "v"

Then the speed of the block must be "v/5"

so kinetic energy of the block will be given as

$K = \frac{1}{2}m(\frac{v}{5})^2$

$K = \frac{mv^2}{50}$

Now power delivered by the external agent is given as

$P = F. v$

$P = \frac{ma}{5} \frac{v}{5}$

$P = \frac{mav}{25}$

Also we can say that work done by external agent on the system of mass is non zero as it is providing power to it

#Learn

Topic : Work energy and power

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