Question

A soccer ball is kicked from the ground with an initial speed of 20.1 m/s at an upward angle of 47.8˚. A player 53.0 m away in the direction of the kick starts running to meet the ball at that instant. What must be his average speed if he is to meet the ball just before it hits the ground? Neglect air resistance.

Answer 1

Answer:3.95 m/s

Explanation:

Given

Initial velocity(u)$=20.1 m/s$

launch angle$=47.8^{\circ}$

Player is 53 m away

Range of projectile

$R=\frac{u^2sin2\theta }{g}$

$R=\frac{20.1^2\times sin95.6}{9.8}$

R=41.02 m

so he need to run 53-41.02=11.98 m

Time of flight of projectile $=\frac{2usin\theta }{g}$

T=3.03 s

thus average speed of boy $s_{avg}=\frac{11.98}{3.03}=3.95 m/s$