Question

a ball is thrown vertically up wards returns to the ground after 30 seconds.find
a the velocity with it was thrown up
b the maximum hight it reaches
c it's position after 8 second ​

Answer 1

Velocity = 147 m/s

Velocity = 147 m/sMaximum height = 1102.5 m

Velocity = 147 m/sMaximum height = 1102.5 mHeight after 8 seconds = 862.4 m

Explanation:

(I)

time required to going the ball up = t¹ and

time required to fall the ball on the ground = t²

t¹ + t² = 30 sec

t¹ = t² = 15 sec

v = 0

v = u + at

0 = u - g(15)

u = 15g = 15 × 9.8 = 147

(II)

v² = u² + 2as

0 = (147)² - 2×9.8×s

s = 147 × 147

2 × 9.8

s = 1102.5 m

(III)

s = ut + 1 × at²

2

= 0 + 1 × 9.8 × 7²

2

= 240.1 m

h = 1102.5 - 240.1

h = 862.4