Question

a player kicks a football at an angle of 30^o with the horizontaland with initial velocity of 19.6m/s . A second player standing at a distance of 20m from the first and in the direction of the kick,starts running to meet the ball, at the instant it is kiked.how far and how fast must he run in order to catch the ball before it hits the ground

Answer 1

we know that

horizontal range

R = u²sin2θ / g

here

u = 19.6 m/s

θ = 30 deg.

and let g = 9.8 m/s²

so,

R = (19.6)²sin60 / 9.8 = 39.2sin60

or

R = 33.94 ~ 34m

so, the other boy has to run another 34 - 20 m ~ 14 m

the time of flight of the ball is

t = 2.u.sinθ/g = 2 x 19.6 x 0.5 / 9.8

or

t = 2 secs

so, the other boy has to reach their in 2.82 s

his speed should be

v = distance travelled / time = 14 / 2 m/s

so,

v ~ 7 m/s