A body is thrown from a height h with speed, u it hits the ground with speed v

Options

A. the value of v is minimum if the body is thrown horizontally
B. the value of v is maximum if the body is thrown vertically upwards
C. the value of v is maximum if the body is thrown vertically downwards
D. The value of v does not depend on the direction in which it is thrown

Answer

D

Explanation

`v_(1)=2m//s ` and `v_(2)=1m//2 `
Initial `K.E. =1/2 mv_(1)^(2)=1/2m xx 4=2m` and K.E. after rebound
`=1/2mv^(2)_(2)=1/2 m xx 1^(2)=m/2`
`therefore` Loses in K.E.
`=1/2 m(v_(1)^(2)-v_(2)^(2))=(2m-m/2) =(3m)/(2)`
Percentage loss of K.E.
`=((1)/(2)m(v_(1)^(2)-v_(2)^(2)))/((1)/(2)mv_(1)^(2))=((3m)/(2))/(2m)xx 100`
`=3/4 xx 100=75%`