Question

a stone is projected vertically upwards with a velocity of 21m/s from 1.5 m above the ground level.
Find: (a) the maximum height above the ground reached by a stone.
(b) the time of flight of the stone
(c) the velocity with which it hits the ground

Answer 1

Answer:

u=21 m/s

h=1.5 m

v=0 m/s

sorry i don't know the answer i tried my best to think really sorry : (

Answer 2

Answer:

• u = 21 m/s
• h1 = 1.5 m

Solution:

(a) v² = u² + 2as

u² = 2 (9.8) s

s = 441 / 2(9.8)

s = 22.5 m

h = h1 + s

= 1.5 + 22.5

= 24 m

Therefore, the height is 24 m.

(b) For s,

v = u + at

0 = 21 - 9.8t

t = 21/9.8 = 2.14 s ... (1)

For h,

h = ut + ½ at²

24 = ½ (9.8) t²

48 = 9.8 t²

t² = 4.9 (approx)

t = 2.21 s ... (2)

From (1) & (2)

T = 2.14 + 2.21 = 4.35 s

(c) u = 0, t = 2.21 s

» v = u + at

v = 9.8 (2.21)

v = 21.66 m/s