1.

A particle of mass `m` is projected at an angle `alpha` to the horizontal with an initial velocity `u`. The work done by gravity during the time it reaches its highest point isA. `u^(2) sin^(2) alpha`B. `(m u^(2) cos^(2) alpha)/(2)`C. `(m u^(2) sin^(2) alpha)/(2)`D. ` - (m u^(2) sin^(2) alpha)/(2)`

Answer» Correct Answer - D
Velocity at top `= u cos alpha`
`W_(m) = DeltaKE = (1)/(2) m(u cos alpha)^(2) -(1)/(2) m u^(2) = -(m u^(2) sin^(2) alpha)/(2)`.


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