Question

A slingshot fires a pebble from the top of a building at a speed of 15.0 m/s. The building is 30.0 m tall. Ignoring air resistance, find the speed with which the pebble strikes the ground when the pebble is fired.
(a) horizontally,
(b) vertically straight up,
(c) vertically straight down.

Answer 1

Answer:

V=28.5m/s

b=V=28.5m/s

c=V=28.5m/s

Explanation:

A slingshot fires a pebble from the top of a building at a speed of 15.0 m/s. The building is 30.0 m tall. Ignoring air resistance, find the speed with which the pebble strikes the ground when the pebble is fired.

(a) horizontally,

(b) vertically straight up,

(c) vertically straight down.

u=15m/s

yi=30m

v=?

yf=0

system=pebble+earth

workdone=0

chnage in energy=0

ki+Ui=Kf+Ui

K=kinetic energy

U=potential energy

1/2mv^2+mgyf=1/2mu^2+mgyi

V^2=u^2+2gyi

V=$\sqrt{15^2+2*9.81*30}$

V=28.5m/s

b. and c will be the same as a. because the magnitude of the kinetic energy is dependent on the velocity and not the magnitude which the pebble is tilted at