A stone is thrown horizontally from the top of a building 12.3 m/s. If the stone strikes the ground after 1.92s. Determine the height of the building and the horizontal distance traveled?

1 Answer
Feb 16, 2018

#"The height of the building is 18.06 meter."#
#"The horizontal distance traveled is 23.616 meter."#

Explanation:

#t = sqrt((2*h)/g)" (variant on Torricelli's law)"#
#=> t² = (2*h)/g#
#=> h = (g*t^2)/2#
#"Here we have :"#
#=> h = 9.8*1.92^2/2 = 18.06 m#
#"The horizontal distance traveled is :"#
#x = v_x*t = 12.3 * 1.92 = 23.616 m#

#t = " time to fall in seconds (s)"#
#h =" height in meter (m)"#
#g = " gravity constant = 9.8 m/s²"#

#"Note that Torricelli's law gives the speed in function of"#
#"the height when falling vertically : "#
#v = sqrt(2*g*h)#
#"But we can also have the time of falling vertically in function"#
#"of the height : "#
#t = sqrt((2*h)/g)#
#"We got the height out of this formula but it is basically nothing"#
#"less than this general formula : "#
#Delta h = h - h_0 = v_{0y}*t - (g*t^2)/2#
#"(minus sign before g because we take + direction as upwards)"#
#"with "v_{0y}" the initial vertical velocity."#
#"Here "v_{0y}" = 0, so we get"#
#Delta h = - (g*t^2)/2#