Question

The system is realeased from rest. 10kg block moves down by 2m. find work done by gravity on 10kg block

Answer 1

A block of mass 2 kg is released from the top of a rough incline of a height of 2 m. If the velocity of the block on reaching the bottom of the incline is 4 m/s, what is the magnitude of work done by the frictional force?



Had there been no frictional force the velocity of the body in a fall of 2m, whether by free fall or sliding along an incline ( because gravitational force is conservative) would have been,

v² - u² = 2 g s, v = velocity achieved in free fall, u = initial velocity = 0 m/s as the body is just released from top of the incline, g = acceleration due to gravity = 10 m/s², s= 2 m.

v² = 2×10×2 = 40 (m/s)²

But velocity as measured = 4 m/s

Energy that would have been if friction was absent = ½ m v² = ½ × 2 kg × 40 m²/s² = 40 Joule

Energy as measured = ½ × 2 kg× 4² m²/s²= 16 Joule

Work done by friction = 40 Joule - 16 Joule = 24 Joule.

So energy lost to friction = 24 Joule

Answer 2

Answer:

200 J

Explanation:

Work done by gravity on 10 kg block=W=mgh

⇒W=10×10×2

⇒W=200J