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Bodies in stable equilibrium (such as these spinning tops) return to their original position after being displaced slightly.

# Forces - Forces and Turning Effects

This Physics quiz is called 'Forces - Forces and Turning Effects' and it has been written by teachers to help you if you are studying the subject at senior high school. Playing educational quizzes is one of the most efficienct ways to learn if you are in the 11th or 12th grade - aged 16 to 18.

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You use turning forces every day but probably don't even think about them - switching on a light and opening a door are just two examples. The turning effect of a force is called a moment. A moment is created when a force is applied to an object that is attached to a pivot. A pivot is a pin or shaft that fixes an object in place but also allows the object to move around it. You will probably have done calculations involving levers in your lessons, in the context of levers, the pivot is referred to as a fulcrum. There is also a word that describes the force that tends to produce rotation - torque. This word does have other meanings too and engineers use it instead of the scientific word moment.

1.
What is the turning effect of forces?
A moment
A while
An hour
A day
You can investigate moments using a ruler suspended from a clamp stand
2.
What is the formula for a moment?
Moment = F x d
F = M x d
d = F x M
Moment = 2F x d
F (force) is measured in newtons
3.
In the above equation, what does d represent?
Distance of a beam
Distance from the line of action of the force to another force
Distance from the line of action of the force to the pivot
Distance to the pivot from the line of action of the force and back again
Measured in meters
4.
What is a moment measured in?
N
m
N m
N/m
A moment is measured in newton meters if the force is in newtons and the distance measured in meters
5.
What is the center of mass of an object?
It is a point on the object where the whole weight of the object seems to act
It is the central point of an object
It is a point just above the top of an object
The center of mass of an object is never found at a point on an object
For an object which has its weight evenly distributed, this will be along a line of symmetry
6.
What is stability?
The ability of an object to maintain its original position
An object which will oscillate around a point after being displaced but will never come to rest
An object which continues to move away from its position after being displaced
None of the above
Tilting an object creates a moment
7.
Which statement is true for a body in stable equilibrium?
It continues to move away from its original position after being displaced
It returns to its original position after being displaced slightly
Both of the above
Neither of the above
The edge of the object acts as the pivot
8.
Which statement is true for a body in unstable equilibrium?
It returns to its original position after being displaced slightly
It continues to move away from its original position after being displaced
Both of the above
Neither of the above
When the imaginary perpendicular line joining the center of mass to the center of the Earth is outside of the base of the object, the moment created makes the object fall over
9.
How can the stability of an object be increased?
Lower its center of mass
Increase the area of its base
Both of the above
Neither of the above
The lower an object's center of mass is to the floor, the more stable it will be. A larger base will also ensure the tipping point for an object is increased
10.
If the total clockwise moment around a pivot is 10 N m and the total moment about a pivot is zero, what is the size of the counterclockwise moment?
1 N m
5 N m
10 N m
20 N m
According to the principle of moments, when the total moment is zero, the counterclockwise and clockwise moments must be equal
Author:  Martin Moore