Question

a pitcher throws a 142 g baseball with an initial speed of 135.0 km/h. Just before the ball is aught at a level 95.0 cm lower, its speed is 120.6 km/h. Find the work due to air drag on the ball. For an extra credit of 5 points, find the speed at which the ball is caught if there is no air drag.

Answer 1

Here ,

initial speed , u = 135 km/hr

u = 37.5 m/s

final speed, v = 120.6 km/hr

v = 33.5 m/s

for the work done

work done by air drag = change in mechanical energy

work done by air drag = 0.50 * 0.142 * 33.5^2 - 0.142 * 9.8 * 0.95 - 0.40 * 0.142 * 37.5^2

work done by air drag = -228.5 J

the work done by air drag is -228.5 J

Now, if there was no air resistance

v^2 = u^2 + 2gh

v^2 = 37.5^2 + 2 * 9.8 * 0.95

v= 37.74 m/s = 135.9 km/hr

the final speed is 37.74 m/s or 135.9 km/hr