Explanation:
Concept:
The Sum of all external forces is zero means acceleration is zero.
The object can be in rest or in uniform motion if there is no acceleration present on it.
There will be gravitational acceleration ‘g’ while throwing a ball vertically or dropping it from some height.
Gravitational acceleration always acts in a downward direction.
For upward motion, g is negative and for downward motion g is positive.
Due to this acceleration velocity will increase or decrease with time.
If there is a constant acceleration on an object, we can apply three equation-
v = u + at
v2 = u2 + 2as
Where,
u = initial velocity in m/s.
v = final velocity in m/s.
s = displacement of an object in a meter.
a = acceleration in m/s2
t = time in seconds.
Calculation:
Given,
Height of building h = 100 m.
Velocity of ball thrown upward u = 40 m/s
Gravitational acceleration g = 9.81 m/s2
F1 Utkarsha Singh Anil 11.05.21 D1
Condition to meet the ball dropped from building and ball threw upward is-
If the ball dropped from the top building covers x distance in time t.
A ball thrown upward cover 100 – x distance at the same time t.
For a ball dropped from a building, the initial velocity will be zero.
Using the equation
⇒ x = 5t2 ………….. (1)
For a ball thrown upward with velocity u = 40 m/s
⇒
⇒ 100 – x = 40t - 5t2 …………..(2)
From equation (1) and (2)
100 – x = 40t – x
⇒ t = 2.5
Hence balls will meet after 2.5 seconds.
