Calculating moments
1. Calculating Moments
What is a Moment?
A moment is the turning effect of a force about a pivot (or point).
Formula
Moment=Force × Perpendicular Distance
Force → measured in newtons (N)
Distance → measured in meters (m)
Moment → measured in newton-meters (Nm)
Key Rules
Distance must be perpendicular to the line of action of the force
If force is closer to the pivot → smaller moment
If force is farther from the pivot → larger moment
Clockwise & Anticlockwise
Clockwise moments turn right
Anticlockwise moments turn left
Principle of Moments (Equilibrium)
If an object is balanced:
Total Clockwise Moments=Total Anticlockwise Moment
Example
Force = 10 N Distance = 0.5 m
2. Calculating Distance
Distance depends on the situation. Here are the main physics cases.
A. Distance from Speed and Time
Formula
Distance=Speed × Time
Speed → m/s
Time → seconds
Distance → meters
Example
Speed = 20 m/s Time = 5 s
Distance=20×5=100 m
B. Distance Using a Speed–Time Graph
Distance = area under the graph
Rectangle → constant speed
Triangle → uniform acceleration
C. Perpendicular Distance (Very Important for Moments)
This is the shortest distance from:
pivot → line of action of force
Not the slanted distance
Always measure at 90°
3. Calculating Force
A. Force from Mass and Acceleration (Newton’s 2nd Law)
Formula
Force=Mass × Acceleration
Mass → kg
Acceleration → m/s²
Force → N
Example
Mass = 4 kg Acceleration = 3 m/s²
B. Force (Weight)
Formula
Weight=Mass × g
g=9.8 m/s2
Example
Mass = 5 kg
W=5×9.8=49 N
C. Force from Moments
Rearranging:
moment
Force= -----------------------
distance
Example
Moment = 20 = 10 N
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