Question

A stone is dropped vertically downwards. What is the velocity of the rock after 4 seconds ? What is the displacement of the rock after 4 seconds ?

Answer 1

Vf = 39.2 m/s

h = 78.4 m

Step-by-step explanation:

Using first equation of motion for vertical motion:

Vf = Vi + gt

where,

Vf = Final Velocity = ?

Vi = Initial Velocity = 0 m/s

g = 9.8 m/s²

t = time taken = 4 s

Therefore,

Vf = 0 m/s + (9.8 m/s²)(4 s)

Vf = 39.2 m/s

Now, we use second equation of motion

h = Vi t + (1/2)gt²

where,

h = height covered = ?

Therefore,

h = (0 m/s)(4 s) + (1/2)(9.8 m/s²)(4 s)²

h = 78.4 m