Question

A body is dropped from a height of 125m and takes some time to reach the ground (g = 10 m/s2). At t=3sec,height of the body from the ground will be..?​

Answer 1

Answer:

Total Distance(S) = 125 m.

Time(t) = 3 seconds.

Initial Velocity(u) = 0

[Since the Body is under free fall.)

Taking g = 10 m/s².

Using the Second Equation of the Motion,

S = ut + 1/2 × at²

S = 0 + 1/2 × 10 × 3² [∵ a = g ]

S = 5 × 9

S = 45 m.

∴ Distance travelled by the Body in First 2 seconds under gravity is 20 m.

Remaining Distance = 125 - 45

= 80m.

Now, Using the Equation of the Motion,

v = u + at

v = 0 + 10 × 3 [∵ a = g ]

v = 30 m/s.

∴ Velocity of the Body under free fall is 30 m/s.

As per as the Question, After 3 seconds Gravity becomes zero.

Thus, Velocity = Displacement/Time.

⇒ Time = Displacement/Velocity.

⇒ Time = 80/30

⇒ Time = 2.6 seconds.

∴ Total time = Time taken to cover a distance of 30 m + Time to cover the distance of 80m.

= 2.6 + 9

= 11.6 seconds.

∴ Total time taken to reach the ground is 11.6 seconds.