Question

A plane is flying horizontally at $98{ms}^{-1}$ and releases an object which reaches the ground in 10 s. The angle made by it while hitting the ground is (in degrees).

• A. ${55}^{}$
• B. ${45}^{}$
• C. ${60}^{}$
• D. ${75}^{}$

Answer 1

The correct option is B ${45}^{}$

X-direction:

Initial velocity $u_x=98m/s$

Time of flight $T=10s$

Final velocity in x-direction $V_x=u_x+a_{x}t$

Or $V_x=98+0=98m/s$

Vertical downward direction :

Initial velocity $u_y=0$

Acceleration $a_y=9.8m/s^2$

Final velocity in y direction $V_y=u_y+gT=0+9.8\times 10=98m/s$

Angle made by velocity with ground $\tan \alpha =\frac{V_y}{V_x}=\frac{98}{98}=1$

$⟹\alpha ={45}^o$

Correct answer is option B.