Question

A body falls freely from a height of 125 m . after 2 sec gravity ceases to act . find the time taken to reach the ground

Answer 1

Hello Dear.

Here is the answer---

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Given Conditions ⇒

Total Distance(S) = 125 m.

Time(t) = 2 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 × 2²   [∵ a = g ]
S = 40/2
S = 20 m.

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

Remaining Distance = 125 - 20
                                  = 105 m.


Now, Using the Equation of the Motion,
 v = u + at
v = 0 + 10 × 2   [∵ a = g ]
v = 20 m/s.

∴ Velocity of the Body under free fall is 20 m/s.

As per as the Question, After 2 seconds Gravity becomes zero.


Thus, Velocity = Displacement/Time.
⇒ Time = Displacement/Velocity.
⇒ Time = 105/20
⇒ Time = 5.25 seconds.


∴ Total time = Time taken to cover a distance of 20 m + Time to cover the distance of 105 m.
                   = 2 + 5.25
                   = 7.25 seconds.


∴ Total time taken to reach the ground is 7.25 seconds.



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Hope it helps.

Have a Good Day.

Answer 2

Here ya go bud

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