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Define weight of an object.
The gravitational force acting on the object
____ = mass x gravity.
Define the mass of an object
The amount of matter in an object
Base quantity measured in kg
Define centre of gravity.
A point where the entire weight of the object appears to act.
Define centre of mass.
A point through which any externally applied force produces straight-line motion without any rotation.
Define the newton
A force that will give a 1kg mass an acceleration of 1ms-2 in the direction of the force
What are the 5 steps for the experiment to find the centre of mass?
What is drag?
The resistive force experienced by an object moving through fluid (liquid or gas).
What are the factors that affect drag?
What happens when an object reaches terminal velocity?
The speed of the object is constant
Objectâs acceleration is zero. (The net force on the object is zero)
Define moment of a force.
The product of the force applied and the perpendicular distance of the line of action of the force from the axis or point of rotation.
The turning effect of a force about some axis or point
What is the equation for moments?
moment = force x perpendicular distance from the pivot.
What is the unit for moment?
Nm (Newton metres)
What are the two conditions for an object in equilibrium?
Resultant force acting on object = 0
Resultant moment acting on object = 0
What is the principle of moments?
The sum of the clockwise moments about a point or an axis is equal to the sum of the anticlockwise moments about the same point or axis.
What is a couple?
Two equal but opposite forces acting on an object.
The forces must be parallel and along different lines.
What is torque?
The moment of a couple
What is the equation for the torque of a couple?
torque of a couple = one of the forces x perpendicular separation between the forces = Fd
What is the torque of a couple the same as?
The total moment of the two forces about their midpoint.
Define density of a substance.
Its mass per unit volume.
How could you determine the density of a substance?
By calculating the mass of the substance and its volume.
Define pressure.
The normal force exerted on a surface per unit cross-sectional area.
What is the unit for pressure?
Nm-2 or Pa
what do the symbols stand for in p= hĎg
h= height
Ď=density of the fluid
g= accel due to gravity.
What is Archimedes' principle.
The upthrust exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.
Principle of moments
For a body in rotational equilibrium, the sum of the anticlockwise moments about any point is equal to the sum of the clockwise moments about that same point.