Download 008 Torque 2 - Equilibrium

g = 9.8 ms-2
5 kg
3 kg
0.4 m
0.6 m
1. How many forces do you see in this system?
2. Calculate the momentum produced by the 5 kg mass.
3. Calculate the momentum produced by the 3 kg mass.
4. Is this system in equilibrium or not? Explain your answer.
5. If the system is in equilibrium, a) find the mass of the
ruler; b) find the support force acting from the pivot.
What is Equilibrium?
Fnet = 0
τnet = 0
Fnet = 0
τnet = 0
It means…
Total
Clockwise
Moments
Total
+ Anticlockwise
Moments
=
0
τnet = 0
Anticlockwise moment = 98 Nm (20 x 9.8 x 0.5)
Clockwise moment = 98 Nm
Net Torque = 0
Fnet = 0
τnet = 0
Is this system at equilibrium?
500 g
200 g
30 cm
70 cm
You may assume:
• The ruler is uniform (i.e. its centre of mass
is exactly at the middle)
• The mass of the ruler = 50g
7.35 N
500 g
200 g
1.96 N
4.9 N
0.49 N
Fnet = 0 total upward force = total downward force
τnet = 0 total clock. torque = total anticlock. torque
Two pivots case
FA
FB
80 kg
0.5 m
Pivot A
0.5 m
1.0 m
Pivot B
294 N
784 N
mass of the plank = 30 kg
length of the plank = 2 m
Torque Exercises
•
Homework Booklet Worksheet #12
(both pages)
•
Extension Work: Activity 9B Q8 ~ 12