Question

15. (a) A stone is dropped from the edge of the roof. (i) How long does it take to fall 4.9 m? (ii) What will be the acceleration after 1 second and 2 seconds? (b) Gravitational force between two objects is 80 N. How should the distance between these objects be changed so that the force between them becomes 40 N?​

Answer 1

Answer:

(a) As the stone is dropped, its initial velocity,u=0,

h=4.9m,a=g=9.8m/s2, time t=?

From h=ut+12gt2,4.9=0+12×9.8t2=4.9t2ort2=4.94.9=1,t=1–√=1s

(b) Finaly velocity,v=? at t=1s

From v=u+gt,v=0+9.8×1=9.8m/s

(c) Let v be Final velocity whenh=7.9m.

From v2−u2=2gh,v2−0=2(9.8)7.9

or v=2×9.8×7.9−−−−−−−−−−−√=154.84−−−−−√=12.4m/s

(d) The accceleration of a freely failling body remains the same at all times, i.e,.

a=g=9.8m/s2, after 1 s and after 2 s.

Explanation: