1.1 Basic physics Flashcards
What are the six base si units?
Mass - kg
Length - m
Time - s
Electric current - A
Temperature - K
Amount of substance - mol
What is a homogenous equation?
- Every equation in physics is homogeneous.
- This means the units are the same on each side of the equation.
What is a scalar quantity?
A scalar is a quantity that has magnitude only.
Some examples of scalar quantities are mass, distance and speed.
What is a vector quantity?
A vector is a quantity which has both magnitude and direction.
Some examples of vector quantities are displacement, velocity, acceleration and force.
What is density?
Density is defined as mass per unit volume.
What is the equation for density?
p=M/v
where:
m = mass of a sample of the material
V = volume of the same sample of the material
What is a moment?
The turning effect of a force is also referred to as moment or torque.
The moment (or torque) of a force about a point is defined as the force × the perpendicular distance from the point to the line of action of the force.
What is the equation for a moment?
moment=F×d
where:
F = force
d = perpendicular distance from the point to the line of action of the force.
The units of moment (or torque) are N m.
What is the principle of moments?
For a system to be in equilibrium, the sum of the anticlockwise moments about a point is equal to the sum of the clockwise moments about the same point.
This is called the principle of moments.
When will an object topple?
When the line from the centre of gravity, vertically downwards, passes outside of the base.
What are the conditions for an equilibrium?
there is no resultant force in any direction
there is no net moment about any point.
