Question

A stone is dropped from the edge of the roof.

(a) how long does it take to fall 4.9m?

(b) how fast does it move at the end of that fall?

(c) what is the acceleration move at the end of 7.9m?

Answer 1

(a)

Given,

Initial velocity, u = 0

Acceleration due to gravity, $g=9.8m/s^2$

Using the second equation of motion,

s =ut +1/2at².

4.9 = 0 + 1/2(9.8)t²

t² = 1 ;

t =1 sec.

(b) Initial velocity, u = 0

Time = t = 1 sec

Acceleration due to gravity, $g=9.8m/s^2$

Using the second equation of motion,

v = u + at

v = 0+ (9.8)1 = 9.8 m/s.

(c) Acceleraion is constant i.e.; acceleration due to gravity, $g=9.8m/s^2$.