3) If the baseball in problem 1 is taken to the top of a 20 meter tall building and dropped, how fast is it travelling just before impact?

Question

question number 1 : 1) A .145 kg baseball can be thrown at 44.7 m/s by a big league baseball pitcher with a killer fastball. That is 100 miles per hour! How much kinetic energy does that baseball have?

Answer 1

3)

We can use the kinematic equations for this problem and assume that acceleration due to gravity is 9.8 m/s². The distance of the drop (height of the building) is 20m. The initial velocity is zero, since it is dropped from rest. We need to find the amount of time it takes to drop so that we can solve for the speed at that point in time

x-x₀ = v₀ * t + a * t²

-20 = 0 * t + (-9.8) * t²

-20 = -9.8 * t²

t = 1.43 s

Now that we know how long it takes to drop, we can find the velocity at that time.

v = v₀ + a * t

v = 0 + (-9.8) * (1.43)

v = -14 m/s

1)

We can use the formula for Kinetic Energy and solve by plugging in the mass and velocity:

E_K = (1/2) m * v²

E_K = (1/2) * 0.145 * 44.7²

E_k = 144.86 kg*m²/s²