Question

A ball is dropped from top of a building 122.5 m high. How long will it take to reach the ground? What will be it's velocity when it strike's the ground?​

Answer 1

Answer:

The final velocity is 49 m/s.

Here, u is initial velocity t is the time taken and g is acceleration due to gravity. as ball is dropped from the top of the building, so u = 0. t = 5 s. Thus, the time taken by the ball to reach the ground is 5 s.

Hope it helps to u....

Answer 2

Given

• A ball is dropped from the top of a building
• Height = 122.5 m

To Find

• Time taken to reach the ground
• Velocity when the ball strikes the ground

Solution

● We shall find the velocity using the third equation of motion and then use the first equation of motion to find the time taken

● v²-u² = 2as [Third Equation of motion]

● v = u+at [First Equation of motion]

━━━━━━━━━━━━━━━━━━

✭ Velocity when the ball strikes the ground

→ v²-u² = 2as

→ v²-0² = 2 × 10 × 122.5

→ v² = 2 × 1225

→ v² = 2450

→ Velocity = 49.5 m/s

✭ Time taken to strike the ground

→ v = u+at

→ 49.5 = 0 + 10 × t

→ 49.5 = 10t

→ 49.5/10 = t

→ Time = 4.95 sec