Question

A footballer kicks a ball at an angle of 45 degrees with the horizontal. If the ball was in the ball was in the air for 10 seconds and lands 4000 metre away determine its initial speed

Answer 1

A footballer kicks a ball at an angle of 45 degrees with the horizontal. If the ball was in the ball was in the air for 10 seconds and lands 4000 metre away determine its initial speed

t = 2u sin45 / a

u = initial speed

a = acceleration

10 = 2 u /(a root2)

u = 5a root2

squaring

u^2 =50a^2

horizontal distance covered = u^2 sin90/a

4000 = u^2/a

u^2 = 4000a

50a^2 = 4000a

a = 80 m/ sqsec

u = 5 × 80 × root2

u = 400 root2

u = 400 × 1.414

u = 565.6 m/s