A stationary ball drops from the bleachers and reaches the ground at 11m/s What is the height of the bleachers? Round to the nearest whole number

Answer 1

One of the kinematic equations of motion is

where "v_f" is the final velocity, "v_i" is the initial velocity, "a" is the acceleration which in this case is the acceleration due to gravity also known as "g" which is -9.8 m/s², "x_f" is the final height and "x_i" is the initial height. We can let v_i = 0 (dropping means it initially was not moving). We can also let x_f = 0 because we want to know the height from the ground up so we can think about the ground as zero height.

So, with the zeros plugged in, the equation becomes v_f² = -2ax_i or x_i = -v_f²/(2a)

Plugging in the numbers, we get:

x_i = -v_f²/(2a)

x_i = -(11)²/(2(-9.8))

x_i = - 121/(-19.6) = 6.2 m