Unit 1.1 Basic Physics Flashcards
What are SI units?
Fundamental (base) units of physical quantities.
What is the SI unit of mass?
Kg (kilogram)
What physical quantity is measured in mol?
Amount of a substance.
What is the SI unit of current?
Amperes (A)
Is the SI unit for temperature?
Kelvin (K) as this is the absolute scale.
What is the SI unit of length?
Metres (m)
What quantity is measured in seconds?
Time.
Are Newtons (N) an SI unit?
No, Newtons are not fundamental. The SI units for force are kg m s^-2 (Since force = mass x acceleration).
Derive the SI units of energy
Kinetic energy = 1/2 x mass x velocity^2
Units = kg x (m/s) x (m/s)
= kg m^2 s^-2
Drive the SI units of force
Force = mass x acceleration
Units = kg x m s^-2
= kg m s^-2
What multiplier is associated with the prefix kilo (k)?
x 1000 (10^3)
What is 1 eV in J?
1eV = 1.6x10^-19 J
Express 6 kWh in joules
6 kW = 6000 J/s. 1 hour = 3600s
6kWh = 6000 x 3600
= 21.6 x 10^6 J
=21.6 MJ
What is meant by a scalar quantity?
A quantity that only has a magnitude.
What is a vector quantity?
A quantity that has magnitude as well as direction.
Is acceleration a vector or scalar quantity?
Vector
Is mass a scalar or vector quantity?
Scalar
What equation is used to calculate density?
Density = Mass/Volume
Density units: kg m^-3
Mass units: kg
Volume units: m^3
What is a moment?
A turning force. Force x perpendicular distance from the point of line of action of the force.
If an object is in equilibrium, the sum of the anticlockwise moments would be…
Equal to the sum of the clockwise moments (principle of moments).
If an object is in equilibrium it means the object is…
Not accelerating. It is either:
- Stationary
- Moving at a constant velocity.
How can the forces acting on an object be shown to be in equilibrium?
- Adding the horizontal and vertical components of the forces acting on it and showing they equal zero.
- Or if there are 3 forces acting on the object you can draw a scale diagram - if the scale diagram forms a closed triangle, then the object is in equilibrium.
What is meant by a couple?
A pair of equal and opposite coplanar forces that have equal magnitude and opposite direction, applied to a body parallel to each other but not along the same line.
What is meant by the centre of gravity?
The point through which all the weight of an object acts. For a uniform object, the centre of gravity is the geometric centre of the object.
