The ratio of speeds of striking for upward and downward projection is:

Options

A. `1:1`
B. `1:sqrt(3)`
C. `1:sqrt(5)`
D. `1:sqrt(7)`

Answer

d

Explanation

For upward:
`v_(xf)=v_(0)cos 30^(@) - g sin 30^(@) T`
`=10 (sqrt(3))/2-10/2 2/(sqrt(3))=5/(sqrt(3))`
`v_(yf)=v_(0)cos 30^(@)=10/2=5m//s`
`v_(f)=sqrt((5/(sqrt(3)))^(2)+5^(2))=10/(sqrt(3))m//s`
For downward:
`v_(xf)=v_(0)cos 30^(@) + g sin 30^(@) T=25/(sqrt(3))`
`v_(xf)=5m//s`
`v_(f)=sqrt((25/(sqrt(3)))^(2)+5^(2))=10sqrt(7/3)m//s`
Ratio =`1:sqrt(7)`