# An object is thrown vertically at a height of #7 m# at #1 m/s#. How long will it take for the object to hit the ground?

##### 1 Answer

Jun 6, 2018

#### Explanation:

Time taken to reach the same height

#t_1 = "2u"/"g"#

#color(white)(t_1) = "2 × 1 m/s"/"9.8 m/s"^2#

#color(white)(t_1) = 0.2041\ "s"#

Velocity when it hits the ground

#"v" = sqrt("u"^2 + "2aS")#

#color(white)("v") = sqrt(("1 m/s")^2 + "(2 × 9.8 m/s"^2 × "7 m)")#

#color(white)("v") = sqrt(138.2)\ "m/s"#

#color(white)("v") = 11.75\ "m/s"#

Further time taken to reach the ground

#t_2 = "v – u"/"g"#

#color(white)(t_2) = "11.75 m/s – 1 m/s"/"9.8 m/s"^2#

#color(white)(t_2) = 1.097\ "s"#

Total time taken

#"T" = t_1 + t_2 = 0.2041\ "s" + 1.097\ "s" = "1.3011 s"#