Question

A ball is dropped from a height of $49m$, the wind blows horizontal and important a constant acceleration of $4.90m{s}^{-2}$ to the ball. Choose the correct statement(s).

• A. Path of the ball is a straight line.
• B. Path of the ball is a curved one.
• C. The time taken by the ball to reach the ground is $3.16s$.
• D. The angler made by the line joining initial and final position (on the ground 1st strike) of the ball with horizontal is greater than ${45}^o$.

Answer 1

Answer: (C), (D)

The time taken by the ball to reach the ground is $3.16s$.
The angler made by the line joining initial and final position (on the ground 1st strike) of the ball with horizontal is greater than ${45}^o$.

$u_x=u_y=0,a_x=4.9m{s}^{-2},a_y=9.8m{s}^{-2}$

So $x=\frac{1}{2}{a}_x{t}^2$, and $y=\frac{1}{2}{a}_y{t}^2$

$\frac{x}{y}=\frac{a_x}{a_y}=\frac{1}{2}$

So path of the ball is a straight line.

Let $t$ be the time taken by the ball to reach ground,

then $49=\frac{1}{2}{a}_y{t}^2\Rightarrow t^2=10\Rightarrow t=3.16s$

$\tan \theta =\frac{a_y}{a_x}=2\Rightarrow \theta ={\tan }^{-1}\left(2\right)$