Equilibrium, Torque, and Energy

Question 1

Equilibrium

Answer 1

No translational (straight line) or angular (rotational) acceleraton.

• Static- zero velocity
• Dynamic - constant velocity

Sum F_upward = Sum F_downward

Sum F_rightward = Sum F_leftward

Question 2

Systems not in Equilibrium

Answer 2

Pretend the system is in equilibrium.

Sum F_upward = Sum F_downward

Sum F_rightward = Sum F_leftward

Since it is not in equilibrium, the two sides are not equal. To balance the two sides, add “ma” to the side with the less force.

ex. Sum F_upward + ma = Sum F_downward

Question 3

Torque

Answer 3

Torque is a twisting force (MCAT definition).

T = Fl(lever arm)

Use following formulae in the given order: the sum of

F_upward = F_downward

F_rightward = F_leftward

T_clockwise = T_{counter-clockwise}