Question

a tennis ball is thrown up and reaches a height of 4.05 M before coming down. What was it's initial velocity? How was total time will it take to come down? The value of g is 10 M per second square

Answer 1

Displacement (s) = 4.05 m

g = -10 m/s² Final velocity (v) = 0 m/s

To find: Initial velocity (u) = ? ttotal (t) = ?

Formulae: v² = u² + 2gs, u + gt

ttotal = 2 × t

Solution: v² = u² + 2gs

0² = u² + 2 × (-10) × 4.05

0 = u² - 81

u² = 81

u = 9 m/s

v = u + gt

0 = 9 + (-10) × t

10 t = 9

t = 0.9 s

Time of ascent = Time of descent ttotal = 2t

= 2 × 0.9 = 1.8 s

The initial velocity was 9 m/s and total time taken to come down, is 1.8 s.