Practicing Success

Target Exam

CUET

Subject

Physics

Chapter

Work Power Energy

Question:

Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m/s. Take g constant with a value 10 m/s2. The work done by the (i) gravitational force and the (ii) resistive force of air is : 

Options:

i) 10 J  ii) -8.75 J

i) - 10 J  ii) - 8.75 J

i) 1.25 J  ii) -8.75 J

i) 100 J  ii) 8.75 J

Correct Answer:

i) 10 J  ii) -8.75 J

Explanation:

According to work energy theorem

wg + w= \(\frac{1}{2}mv^2\)

w= mgh

     =10-3 x 10 x 103

     = 10J

 10 +  w=\(\frac{1}{2}\) x 10-3 x 50 x 50

 10 +  w= 1.25

w= -8.75J