A) 2s
B) 3s
C) 4s
D) 5s
Correct Answer: B
Solution :
Velocity acquired by the ball after 2 s of drop is \[v=gt=10\times 2=20\text{ }m\text{ }/\text{ }s\] Height fallen by the ball is \[h=\frac{1}{2}g{{t}^{2}}=\frac{1}{2}\times 10\times 4=20\,m\] After gravity disappears, speed is constant. \[\Rightarrow \] \[H-h=(v)\times t\] \[\Rightarrow \] \[80-20=(20)\times t\] \[\Rightarrow \] \[60=20t\]or\[t=3s\]You need to login to perform this action.
You will be redirected in
3 sec