A ball is gently dropped from a height of 20m. If its velocity increases uniformly at the rate of  10 m/s² , with what velocity will it strike the ground? After what time will it strike the ground?

 -Shresthi Goyal, Subject Matter Expert at Edumarz 

Answer: 

Since, it was at rest, therefore, u = 0 

Distance covered (s) = 20m 

Acceleration (a) = 10 m/s²

 v=?

 t=?

By third equation of motion, v² – u² = 2as 

v² – 0 = 2 ×10 × 20

v²= 400 

v =√400= 20 m/s

By first equation of motion,

v = u + at

Substituting the values,

20=0 + 10t

20/10 = t 

t = 2 seconds.