A cat\'s crinkle ball toy of mass 37 g is thrown straight up with an initial spe

Question

A cat's crinkle ball toy of mass 37 g is thrown straight up with an initial speed of 4 m/s. Assume in this problem that air drag is negligible. (a) What is the kinetic energy of the ball (in J) as it leaves the hand? _ (b) How much work is done (in J) by the gravitational force during the ball's rise to the peak? _______ What is the charge in the gravitational potential energy of the ball (in J) during the rise to its peak? (d) If the gravitational potential energy is taken to be zero at the point where it leaves your hand, what is the gravitational potential energy (in J) when it reaches the maximum height? (e) If the gravitational potential energy is taken to be zero at the maximum height the ball reaches, what would the gravitational potential energy (in J) be when it leaves the hand? (f) What is the maximum height the ball reaches(in m) _____ m

Explanation / Answer

(A) KE = m v^2 /2

KE = (37 x 10^-3 kg) (4 m/s)^2 /2

KE = 0.296 J

(B) As ball reaches to its maximum height its KE = 0

so work done by gravity= change in KE

Wg = 0 - 0.296 = - 0.296 J

(c) change in PE = - work done by gravity

= 0.296 J

(d) PEf - PEi = change in PE

PEf - 0 = 0.296

PEf = 0.296 J

(e) 0 - PEi = 0.296

PEi = - 0.296 J

(f) PE = m g h

0.296 = (37 x 10^-3)(9.81)(h)

h = 0.815 m

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