Question

A body is thrown vertically upward. The acceleration is 10 m/s^2. If it reaches a maximum height
of 20 m, find the velocity at which it was thrown.
15 m/s
12 m/s
18 m/s
20 m/s

Answer 1

Required Answer :

• The final velocity of the ball = 20 m/s

Given :

• Acceleration of the ball = 10 m/s²

• Maximum height reached by the ball = 20 m

• Initial velocity of the ball = 0 m/s [Because the ball comes to at rest at the topmost point and it's initial velocity becomes zero and its velocity starts to increase when it falls downward.]

To find :

• Final velocity of the ball

Solution :

Here, we shall use the third equation of motion to calculate the final velocity of the ball.

Third equation of motion :-

• v² - u² = 2as

where,

• v denotes the final velocity
• u denotes the initial velocity
• a denotes the acceleration
• s denotes the distance/displacement/maximum height reached

we have,

• Final velocity (v) = ?
• Initial velocity (u) = 0 m/s
• Acceleration (a) = 10 m/s²
• Maximum height reached (s) = 20 m

Substituting the given values :-

→ v² - (0)² = 2(10)(20)

→ v² = 2 × 10 × 20

→ v² = 400

→ Taking square root on both the sides :-

→ v = √400

→ v = √(20 × 20)

→ v = 20

Therefore, the final velocity of the ball = 20 m/s