# Solve these numericals:- (PLEASE HELP, URGENTLY NEEDED!)1) A stone is dropped from a tall building of 80 metres height. Find its final velocity and the time taken to touch the ground (take g = 10 metres per second square). 2) A car initially at rest starts moving with an acceleration of 0.5 metres per second square and travels a distance of 25 metres. Calculate its final velocity and its time.

1
by reishumwi

2015-04-30T18:34:49+05:30

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1)
s = 80 m = displacement
u = 0  = initial velocity
g = 10 m/sec/sec  acceleration of the stone

equation of motion :  v² = u ² + 2 a s
v² = 0 + 2  * 10 * 80 = 1600
v = final velocity = 40 m/sec

2)    u = 0
a = 0.50 m/sec/sec
s = 25 m
v² = u² + 2 a s
= 0 + 2 * 0.4 * 25  = 20
v = √20 m /sec = 2 √5 m/s

v = u + a t
t = (v - u) / a = 2√5 / 0.50  = 4 √5  seconds.

sorry. in (2) v² = u² + 2 a s => v² = 2 * 0.5 * 25 => v = 5 m/s
t = 5/0.50 = 10 sec
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