A 0.5 kg ball thrown directly upward with an initial speed of 18 m/s reaches a m

Question

A 0.5 kg ball thrown directly upward with an initial speed of 18 m/s reaches a maximum height of 7.6 m. As the ball moves upward, the air exerts a drag force on the ball throughout the flight. (a) When the ball travels from the release point to maximum height, does the mechanical energy of the ball-Earth system increase, decrease, or remain the same?

__Remain the same ___Decrease ___ Increase

(b) What is the change in kinetic energy of the ball when it travels from the release point to maximum height?
______J

(c) What is the change in potential energy of the ball-Earth system when the ball travels from the release point to maximum height?
_____J

(d) What is the work done by air resistance when the ball travels from the release point to maximum height?
____J


(e) What is the average force due to air resistance?
_____N

(f) When the ball returns to the release point, its speed will be

___Less than 18 m/s ____ Greater than 18 m/s____     Equal to 18 m/s

Explanation / Answer

Answer for

a) decrease due to air resistance

b)at maximum height k.e is zero

so 1/2 mv2-0 = 1/2*0.5*18*18=81J

c)o.e=mgh=0.5*9.8*7.6=37.24 J

d)Work done by air resistance = - loss in energy

=-(81-37.24)=-43.76J

e) F=workdone by air resistance/height

= 43.76/7.6=5.757 N

f) less than 18

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