Question

A ball is dropped from the top of a building of height 80 m. At same instant another ball is thrown upwards



with speed 50 m/s from the bottom of the building. The time at which balls will meet is



(1) 1.6 s (2) 5 s (3) 8 s (4) 10 s

Answer 1

Answer:

a)1.6 seconds

Explanation:

1 st case:

h=80m

u=0

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

(h=4.9t^2) this equation 1

2 nd case:

80-h=ut-(1/2)gt^2

u=50 m/s

so,

(80-h=50t-4.9t^2) this is equation 2

now,

add equation 1 and 2

80-h+h=50t-4.9t^2+4.9t^2

80=50t

t=80/50

therefore t=1.6