A ball rolls over the edge of a platform with only a horizontal velocity.The height of the platform is 1.6 m and the horizontal range of the ball from the base of the platform is 20 m.What is the horizontal velocity of the ball just before it touches the ground? Neglect air.
A)35 m/s
B)9.8 m/s
C)20 m/s
D)4.9 m/s
E)70 m/s

Question

Quizplus · Accepted Answer

The horizontal velocity of the ball is constant throughout its flight. The vertical velocity of the ball is zero when it leaves the platform and increases as it falls. The horizontal range of the ball is equal to the horizontal velocity multiplied by the time of flight. The time of flight can be found using the vertical motion equation:$$y = vi*t + 1/2*a*t^2$$where y is the vertical displacement, vi is the initial vertical velocity, a is the acceleration due to gravity, and t is the time of flight.Substituting the given values into the equation, we get:$$-1.6 = 0 + 1/2*(-9.8)*t^2$$Solving for t, we get:$$t = 0.632 s$$The horizontal velocity of the ball is then:$$v = d/t = 20 m / 0.632 s = 31.6 m/s$$The closest answer choice is A) 35 m/s.

A Ball Rolls Over the Edge of a Platform with Only