Question
Physics Question on Work-energy theorem
An object of mass 10kg falls from rest through a vertical distance of 10m and acquires a velocity of 10m/s .The work done by the push of air on the object is (g=10m/s2)
A
500 J
B
- 500 J
C
250 J
D
- 250 J
Answer
- 500 J
Explanation
Solution
Given, mass of object =10kg
Initial velocity (rest), u=0
Final velocity, v=10m/s
g=10m/s2
Work done by air =−( Work done by the object to cover the vertical distance)
=−F×s=−mgh[as,v2−u2=2gh⇒gh=2v2−u2]
=−10×2(102−02)=−210×10×10=−500J