Physics Word Problem Please?
A slingshot fires a pebble from the top of a building at a speed of 14.0 m/s. the building is 31.0 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.
- RealProLv 72 months agoFavorite Answer
Have you been taught the conservation of energy?
Change in potential energy is the same no matter how it gets there.
Given no change in total mechanical energy,
v = sqrt(14^2 + 2*9.81*31) m/s
If not then use kinematics formulas.
- oldschoolLv 72 months ago
You have to memorize trajectory equations.
Vyf² = 0²+2*g*d = 19.6*31 = 24.65 at impact
Vxf = 14m/s at impact so
Vf² = 24.65²+14² = 28.3m/s at impact a)
Vo straight up
Find time of flight
31 +14*t - 4.9*t² = 0
t = 4.32
Vy(4.32) = 14 - 9.8*4.32 = -28.3m/s (down) at impact b)
Vo straight down
Vyf² = 14²+19.6*31 = 28.3²
28.3m/s (down) at impact c)
- Anonymous2 months ago
a) 28 m/s
b) 28 m/s
c) 28 m/s
Gravity is a conservative field