How fast was the ball going when it left Josh’s hand (the initial velocity)? (full question in description)

Question

PRE-APJosh rolled a bowling ball down a lane in 2.5 s. The ball traveled at a constant

acceleration of 1.8 m/s 2 down the lane and was traveling at a speed of 7.6 m/s by the time it

reached the pins at the end of the lane. How fast was the ball going when it left Josh’s hand (the

initial velocity)?

Answer 1

You are given 3 variables:

t = 2.5 s

a(acceleration) = 1.8 m/s²

v_f (final velocity) = 7.6 m/s

Unknown variable

v_i(initial velocity) = ?

Since acceleration is constant, use a kinematic equation:

Since you aren't given distance, choose the equation with initial velocity without d(distance), the lower left equation. substitute your numbers and solve for v_i

v_i = v_f - at = 7.6 m/s - (1.8 m/s² x 2.5 s) = 3.1 m/s