Question

A man can throw a stone 80 m. The maximum height to which he can raise the stone is

• A. 10 m
• B. 15 m
• C. 30 m
• D. 40 m

Answer 1

Answer: (D)

40 m

Answer 2

The problem is different from problem no. (54). In that problem for a given angle of projection range was given and we had find maximum height for that angle.

But in this problem angle of projection can vary, ${R\frac{u^{2}}{g}}_{\max}$ [for $\theta = 45{^\circ}$]

But height can be maximum when body projected vertically up ${H\frac{u^{2}\sin^{2}90^{o}}{2g}}_{\max} = \frac{u^{2}}{2g} = \frac{1}{2}\left( \frac{u^{2}}{g} \right)$= 40 m