I could not care less how massive the rock is.
Hi = height of building
Vi = initial v up = 10.5 sin 40 = 6.75 m/s
u = constant horizontal speed = 10.5 cos 40 = 8.04 m/s
x = 19.6 = u t = 8.04 t
so t = time aloft = 19.6 / 8.04 = 2.44 seconds
h = Hi + Vi t - 4.9 t^2
0 = Hi + 6.75 * 2.44 - 4.9 * 2.44^2
solve for Hi
A 0.65 kg rock is projected from the edge of
the top of a building with an initial velocity of
10.5 m/s at an angle 40◦
above the horizontal.
Due to gravity, the rock strikes the ground at
a horizontal distance of 19.6 m from the base
of the building. How tall is the building? Assume the
ground is level and that the side of the building is vertical. The acceleration of gravity is
9.8 m/s
2
.
Answer in units of m
1 answer
1 answer