Question

Difficulty: MediumProjectile Motion

A projectile is launched from level ground with an initial speed of 25 m/s25\text{ m/s} at an angle θ\theta to the horizontal such that sinθ=0.80\sin\theta = 0.80. Calculate the maximum height reached by the projectile in meters. [Take g=10 m/s2g = 10\text{ m/s}^2]

Answer: 20 m

Answer

The maximum height reached by the projectile is 20 m20\text{ m}.
The vertical component of the initial launch velocity is uy=usinθ=25×0.80=20 m/su_y = u \sin\theta = 25 \times 0.80 = 20\text{ m/s}. Using the equation for maximum height H=uy22gH = \frac{u_y^2}{2g}, we substitute uy=20 m/su_y = 20\text{ m/s} and g=10 m/s2g = 10\text{ m/s}^2 to obtain H=40020=20 mH = \frac{400}{20} = 20\text{ m}.

Step-by-Step Solution

1
Calculate the initial vertical velocity component (uyu_y)
uy=25 m/s×0.80=20 m/su_y = 25\text{ m/s} \times 0.80 = 20\text{ m/s}
Only the vertical component of velocity determines the maximum height reached.
2
Calculate the maximum height (HH) using kinematic equations
H=uy22g=2022×10=20 mH = \frac{u_y^2}{2g} = \frac{20^2}{2 \times 10} = 20\text{ m}
At maximum height, the vertical component of velocity becomes zero.

Key Concept

Maximum height of a projectile depends entirely on its initial vertical component of velocity and acceleration due to gravity.
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