Question

A fisherman lifts a fish of mass 250g from rest through a vertical height of 1.8 m, the fish gains a speed of 1.1 m/s. What is the energy gained by the fish?
A. 0.15 J
B. 4.3 J
C. 4.4 J
D. 4.6 J

Answer 1

Hint: The motion is in one dimension. No external force is acting on the system and the only force which acts is the gravitational force and the body moves both upside under the influence of gravitational force. Acceleration due to gravity is taken to be g.

Complete step by step answer:
Mass of the fish= 250 g= \[0.25kg\]
Distance covered by the fish = 1.8 m
Speed gained by the fish = 1.1 m/s
The fish was initially at the rest, so by using Newton’s equation of motion, we can solve this problem.
Potential energy gained \[=mgh\]
$
  = mgh \\
  = 0.25\times 9.8\times 1.8 \\
  = 4.4 J \\ $

So, the energy gained by the fish on account of its position is 4.4 J. So, the correct option is (C).

Additional Information:
When a body is thrown upwards then always at the topmost point the body takes a momentarily pause and when it starts to come back down towards the earth, in this case, the initial velocity is taken as zero and body strikes the earth back with some velocity.

Note:
While doing such kind of problems we have to keep in mind the number of variables which needs to be introduced and what are the given quantities. Also, we have to specifically keep in our mind whether we have to use equations of constant motion or it involves the use of acceleration.