Question

Hola mate :-)
q.1 Certain force acting on a 20kg mass changes its velocity from 3m/s to 2m/s . Find the work done by force.

q.2 A man pull a bucket of water of total mass of 5kg from a well which is 10m in 10s, Calculate the power used by the man.

My answers are -50J and 50 watt respectively....✌

What about urs?

Answer 1

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Ans 1) Mass, m = 20 kg

Initial velocity, u = 5 m/s

Final velocity, v = 2 m/s

Time, t = 1s

From first equation of motion 
       
       v = u + at

or, a = (v - u)/t 
 
a = (2 ms-1 - 5 ms-1)/15


a = -3 ms-2

From third equation of motion,
 

v² - u² = 2as
⇒ (2ms-1)² - (5ms-1)² = 2 x (-3ms-²) x s



⇒   -21 m²s-² = -6 ms-² x s

⇒ s = 7/2 m

Work done = F x s

Force = m x a

Therefore,
 
W = m x a x s
    = 20 kg x (-3ms-²) x 7/2 m
   = -210 Joules


Answer 2) is in attachment see up⤴⤴⤴

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