Question

I have a tennis ball launcher. The launcher will release the tennis ball from rest at a height of 0.5 meters. The Tennis ball needs to travel 15 feet. That is all the information i have. I assume that i can choose what angle to launch.I am lost on where to begin projectile motion and energy calculations.

Answer 1

I think the launcher lauches the ball in horizontal direction from a height, h = 0.5 m

so, initial velocity in y-direction, voy = 0

now we need to find initial horizontal velocity of the tennis ball to move 15 feets before hitting the ground.

horizontal distance travelled, x = 15 feet

= 15*0.3048 m (since 1 feet = 0.3048 m )

= 4.572 m

let t is the time taken for the tennis ball to hit the ground.

use,

-h = voy*t - (1/2)*g*t^2

-h = 0- (1/2)*g*t^2

t = sqrt(2*h/g)

= sqrt(2*0.5/9.8)

= 0.3194 s

so, vox = x/t

= 4.572/0.3194

= 14.3 m/s <<<<<<<<----------------Answer

please comment for further help.