Question

A tower of length 100 meter from which a stone takes 6 seconds to fall at ground.What will be it's velocity at 5 seconds​

Answer 1

Answer:

50 m/s

Explanation:

height of the tower is 100 meters total time is 6 seconds it is a free fall so initial velocity is 0 acc is +10 m/s_2

so we can use kinematic equation v=u+at putting all the values we get 50 m/s

we have to find velocity after 5 seconds so t=5

then we get 50 m/s

Answer 2

Answer:

Use energy conservation

Use energy conservationLet initial velocity u . then

$v(6) = u + gt = u + 60 \\ v(5) = u + 50$

now

$\frac{1}{2} m {u}^{2} + mgh= \frac{1}{2} m(v(6)) {}^{2}$

${u}^{2} + 2 \times 10 \times 100 = (u + 60) {}^{2} \\ 60(2u + 60) = 2000 \\ u = \frac{50}{3} - 30 = \frac{ - 40}{3} \frac{m}{s}$

**Negative sign shows stone was thrown in upward direction .

So

$v(5) = u + 50 = \frac{ - 40}{3} + 50 = \frac{110}{3} \: \frac{m}{s}$