Question

7) You throw a 12-N stone vertically into the air from ground level. You observe that when it is 15.0 m above the ground, it is traveling at 25.0 m/s upward. Use the work –energy theorem to find (a) the stone’s speed just as it left the ground and (b) its maximum height.
8) A 6.0-kg block initially at rest is pulled to the right along a frictionless, horizontal surface by a constant horizontal force of 12 N. Use the work-kinetic energy theorem to find the block’s speed after it has moved 3.0 m.

Answer 1

7a. V^2 = Vo^2 + 2g*h
Vo^2 = V^2 - 2g*h = 25^2 + 19.6*15 = 919
Vo = 30.32 m/s.

7b. h = -(Vo^2)/2g = -(30.32^2)/-19.6 =
46.9 m.

8. a = F/m = 12/6 = 2 m/s^2

V^2 = Vo^2 + 2a*d
Vo = 0,
a = 2 m/s^2
d = 3 m.
Solve for V.