A ball is thrown horizontally from a height of #24 m# and hits the ground with a speed that is five times its initial speed. What is the initial speed?
1 Answer
Apr 2, 2018
Explanation:
Let the initial speed be
Horizontal component of velocity when it hits the ground is
#"v"_"x" = "u"#
If
#"v"_"y"^2 = "2gH" = "2 × 9.8 m/s"^2 × "24 m" = 470.4\ "m"^2//"s"^2#
Final speed of object
According to question
#sqrt("u"^2 + 470.4) = 5"u"#
Squaring on both the sides
#"u"^2 + 470.4 = "25u"^2#
#24"u"^2 = 470.4#
#"u"^2 = 470.4/24 = 19.6#
#"u" = 14/sqrt(10)\ "m/s" = "4.43 m/s"#