A stone that is dropped freely from the rest traveled half the total height in the second. with what velocity will it strike the ground

Respuesta :

The stone will strike the ground with velocity of 33.5 m/s.

What is velocity:

  • Velocity is the directional speed as an indication of its rate of change in position observed from a particular frame of reference.
  • velocity formula is basically displacement divided by time.

What is displacement:

  • It is an vector quantity with magnitude and direction.
  • It defines as the change in position of an object.

Here,

Stone is dropped freely from rest, so it's Initial velocity will be zero.

u = 0 m/s

displacement is equal to half of total height.

y = h/2

since Stone is dropped freely, a=g ( acceleration of gravity)

According to Newton's equation of motion:

y = u* t + 1/2 (at^2)

h/2 = 0 + 1/2 (gt^2)

h = g* t^2 -----1

now at t= t+1 , displacement y = h

h = u* t + ½ g (t + 1)²

h = ½ g (t + 1)² -----2

comparing both equations,

g* t^2 = ½ g (t + 1)²

2t² = (t + 1)²

2t² = t² + 2t + 1

t² − 2t = 1

t² − 2t + 1 = 2

(t − 1)² = 2

t − 1 = ±√2

t = 1 ± √2

Since t > 0, t = 1 + √2.  

So t+1 = 2 + √2.

At that time, the speed is:

v = at + u

v = g (2 + √2) + 0

v = g (2 + √2)

If g = 9.8 m/s²,

v = 33.5 m/s.

The stone will strike the ground with velocity of 33.5 m/s.

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