Basic Classical Mechanics

SI Base Units

Measure Name Symbol Definition
length metre m
mass kilogram kg The mass of 10cm3 of water.
time second s

SI Other Units

Measure Name Symbol Definition
speed metres per second m/s How many metres an object travels every second.
acceleration metres per second squared m/s2 How many m/s an object accelerates per second, or m/s/s.
force newton N How much force a one kilogram object needs to accelerate from 0 to 1 m/s in one second; kg×m/s2
impulse newton second N×s or kg×m/s How much momentum an object has.
energy joule J A newton applied until any object has moved 1 metre is to give it a joule of energy; kg×m2/s2.

Variables in a Linear Push

These are all the variables when, in a completely empty vacuum, an object is pushed from zero velocity for a certain amount of time with a constant force.

Note: variables in bold or italic bold are vectors.

Name Symbol Measure Unit Definition
force F force N The constant amount of force applied to an object during the time when it is pushed.
mass m mass kg The mass of the object being pushed.
time t time s The time during which the object is being pushed.
acceleration a acceleration m/s2 How much that object is accelerating at any given time while being pushed.
initial velocity u velocity m/s The beginning velocity of the object.
final velocity v velocity m/s The final speed and direction of the object after being pushed.
displacement s length m The distance and direction the object has moved once the push has finished (however, the object will continue moving linearly).
kinetic energy KE energy J The amount of energy an object contains.
work W energy J How much energy is required to push the object (in our case seeing as there are no other factors, the same as KE).
momentum p impulse kg×m/s The speed an object has relative to its mass; with two objects of different mass and same velocity, the lighter one will have lower momentum. The total amount of momentum in the universe never changes.


F = ma

v = u + at

s = ut + ½at2

KE = ½mv2

W = Fs

p = mv