The boy plays solitary seesaw as shown. We can understand this by ...

[mpobi80]

The boy plays solitary seesaw as shown. We can understand this by imagining that he has an invisible partner who is actually at the
 
  1) fulcrum.
  2) right end of the board.
  3) rotational inertia of the seesaw as a whole.
  4) seesaw's center of gravity.
 
  Since the seesaw is not rotating, we can say that
  5) the net torque on the seesaw is zero.
  6) potential energy and kinetic energy are equal to each other.
  7) the boy's and the seesaw's centers of gravity must be equal distances from the fulcrum.
  8) the boy and the seesaw must have the same weight.

Question 2

The center of gravity for each truck is marked X. Which truck(s) will tip over?
 
  1) Truck 1
  2) Truck 2
  3) Truck 3
  4) All will tip.
 
  This is because
  5) its center of gravity is highest.
  6) its center of gravity is lowest.
  7) its center of gravity lies beyond a point of support.
  8) all the centers of gravity lie above the wheelbases.

[bigsis44]

Answer to Question 1

Answer: 4, 5

Answer to Question 2

Answer: 3, 7

[mpobi80]

Excellent

[Alyson.hiatt@yahoo.com]

Gracias!