Question

when a ball is thrown vertically upwards it goes through a distance of 19.6 mfind the initial velocity of ball and time takenbu to rise the highest point

Answer 1

let initial velocity = u m/s
time taken to rise to highest point = t second
final velocity at highest point = 0
g = -9.8 m/s²
distance travelled = 19.6 m

d = (v² - u²)/2a
⇒ 19.6 = (0 - u²)/2×(-9.8)
⇒ 19.6 = u²/19.6
⇒ u² = 19.6×19.6
⇒ u = 19.6 m/s

v = u+at
⇒ 0 = 19.6 - 9.8t
⇒ 9.8t = 19.6
⇒ t = 19.6/9.8
⇒ t = 2s

Initial velocity = 19.6 m/s
time taken to reach highest point = 2s

Answer 2

h = 19.6 m

g = - 9.8 m/s²

Since it has to reach at the highest poing where v = 0 ,

using ,

v²-u² = -2gh
b
u² = 2gh

u² = 2gh = 2×9.8×19.6

u = 19.6m/s

Since , also ,

v = u+gt

0 = -3+a 9.8 ×t

t = 19.6/9.8

t = 2 s