CIE IGCSE Physics (0625) - Forces in equilibrium Flashcards
(24 cards)
What is the moment of a force?
The turning effect of a force about a pivot.
What is the equation for moment?
Moment = force × perpendicular distance from the pivot (M = F × d). The distance is measured from the pivot to the line of action of the force.
What are the units of moment?
Newton metre (Nm), the SI unit of moment.
What two factors affect the size of a moment?
The magnitude of the force and its perpendicular distance away from the pivot.
How can a student increase the moment when using a spanner?
Apply a greater force or use a longer spanner.
State the principle of moments.
For an object in equilibrium, the total clockwise moment equals the total anticlockwise moment.
When is a moment considered clockwise?
When it tends to rotate an object in the clockwise direction.
What is the effect of a moment acting anticlockwise?
It causes rotation in the anticlockwise direction.
What does a balanced beam suggest about the moments acting on it?
The total clockwise and anticlockwise moments are equal.
How can you calculate force from a known moment and distance?
Force = moment ÷ perpendicular distance
What are the conditions for equilibrium?
No resultant force and no resultant moment on the system.
What is meant by resultant moment?
The net moment after accounting for all turning effects on an object, acting in the clockwise or anticlockwise direction.
What happens when the resultant moment is zero?
The object does not rotate; it is in equilibrium.
What happens when the resultant force is zero?
The object is either stationary or moving at constant velocity.
What is a practical example of a moment in equilibrium?
A see-saw balanced with equal moments on either side.
What is the centre of mass?
The point where the entire mass of an object can be considered to act.
What is meant by stability?
The tendency of an object to return to its original position after being slightly tilted.
What is a lamina?
A flat, two-dimensional object with negligible thickness.
What is the centre of gravity?
The point at which the entire weight of an object appears to act.
What is a plumb line?
A string with a small mass at the end used to draw vertical lines when finding the centre of gravity.
How can you find the centre of gravity of a lamina?
Suspend the irregularly shaped lamina from two or more different points and draw vertical lines. The point where the lines cross is the centre of gravity.
How can you find the centre of gravity of an irregularly shaped lamina?
A plumb line is used to mark vertical lines from suspension points on an irregularly shaped lamina.
Why does a wide base increase stability?
It keeps the line of action of the object’s weight within its base, which creates a moment that returns the object to its original position when slightly tilted.
Why does packing heavier items at the bottom of a wheeled suitcase improve stability?
It lowers the centre of gravity, making the suitcase less likely to topple over when tilted.
