It's D) valid and testable.
m = mass of the roller coaster = 500 kg
h = height of the hill = 80 m
v = speed of the roller coaster at the bottom of the hill = ?
using conservation of energy
kinetic energy at the bottom of the hill = potential energy at the top of hill
(0.5) m v² = m g h
(0.5) v² = g h
inserting the values
(0.5) v² = (9.8) (80)
v = 39.6 m/s
hence the speed at the bottom comes out to be 39.6 m/s
Answer:
Abby is standing (4.5^2 + 2.3^2)^1/2 from the far speaker
D2 = 5.05 m from the far speaker
The difference in distances from the speakers is
5.05 - 4.5 = .55 m (Let y be wavelength, lambda)
n y = 4.5
(n + 1) y = 5.05 for the speakers to be in phase at smallest wavelength
y = .55 m subtracting equations
f = v / y = 340 / .55 = 618 / sec should be the smallest frequency
