P3.2 Using physics to make things work Flashcards
What is the centre of mass?
The centre of mass is that point at which the mass of the object may be thought to be concentrated
If freely suspended, an object will…
Come to rest with its centre of mass directly below the point of suspension
What is the centre of mass of a symmetrical object?
Along the axis of symmetry
What is the equation for a simple pendulum?
1
T = ——
f
What does the T stand for?
Periodic time in seconds
What does the f stand for?
Frequency in hertz, Hz
What does the time period depend on?
The length of the pendulum
What is the moment?
The turning effect of a force
What is the equation for the size of moment?
M = F x d
What does the M stand for?
Moment of the force in newton metres, Nm
What does the F stand for?
Force in newtons
What does the d stand for?
The perpendicular distance from the line of action of the force to the pivot in metres
If an object is turning, the total clockwise moment must be…
Exactly balanced by the total anticlockwise moment about any pivot
If the line of action of the weight of an object lies outside the base of an object there will be…
A resultant moment and the body will tend to topple
What are some examples of pendulums?
swings at playgrounds, some fairground rides, the inside mechanisms of some clocks - eg grandfather clocks
What is the stability of an object affected by?
the width of the base of the object, the height of its centre of mass
What happens when someone uses a lever?
They a exert a force (the effort) around a pivot to move an object (the load)
When an object moves in a circle it…
Continuously accelerates towards the centre of the circle
What does the acceleration change?
The direction of motion of the body, not the speed
What is the resultant force causing this acceleration called?
The centripetal force
Where is the centripetal force always directed to?
The centre of the circle
The centripetal force needed to make an object perform circular motion increases as the mass…
Of the object increases
The centripetal force needed to make an object perform circular motion increases as the speed…
Of the object increases
The centripetal force needed to make an object perform circular motion increases as the radius…
Of the circle decreases
