6. A 2.00-kg rock is released from rest at a height of 30.0 m. Ignore air resist

Question

6. A 2.00-kg rock is released from rest at a height of 30.0 m. Ignore air resistance and determine (a) the kinetic energy at 30.0 m. (b) the gravitational potential energy at 30.0 m, (c) the total mechanical energy at 30.0 m, (d) the kinetic energy at 0 m, (e) the gravitational potential energy at 0 m, and (f) the total mechanical energy at 0 m. ( 6 pts,) A person in a kayak starts paddling, and it accelerates from 0 to in a distant a; of 0.62, nt. If the combined mass of the person and the kayak is 85 kg, what is the magnitude of the net force acting on the kayak?

Explanation / Answer

a) KE at h = 30 m

KE = 0

b) PE at H = 30 m

PE = mgh = 2*9.8*30 = 588 J

c) TE = PE + KE = 0 + 588 = 588 J

d) h= 0

KE = 0.5*mv^2

v^2 = 2gh

KE = 0.5*2*2gh = 588 J

e) PE at h=0

PE = mgh = 0

f) TE +PE + KE = 588 J

7) s = ut + 0.5*at^2

0.62 = 0 + 0.5*a*1^2

a = 1.24 m/s^2

F = ma = 85*1.24 = 105.4 N

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