Topic 1 Forces And Motion Flashcards
Newtons first law of motion
An object remains at rest, or moves in a straight line at constant speed, unless it is acted on by an unbalanced force.
Speed equation
Speed(v) = distance(d) / time(t)
Equilibrium definition (force)
Any object that is subject to balanced forces is said to be at equilibrium.
Static equilibrium definition
When an object remains at rest.
Dynamic equilibrium definition
If an object is moving with a constant speed and direction.
Weight definition
The force due to gravity close to the surface of the earth is known as weight and has a magnitude given by:
Weight = mass x acceleration due to gravity (W = mg)
Units m/s^2
Earths gravity is 9.81 m s^-2
Hooke’s law
Applied force = constant x extension (Fstr = ks x)
The spring constant quantifies the size of extension produced by a given force.
Rearranged:
ks = Fstr / x
Free body diagrams
A way of presenting all the forces acting on a single object, without the clutter of any surrounding objects.
Arrows point away from the object in the direction the force is being applied. Equal forces require equal sized arrows.
Normal reaction force definition
The reaction force that keep a solid object from falling through the surface it sits on. The force is perpendicular to the surface.
When an object is placed on a surface it compresses the atoms of the surface together. This acts like a sort of spring that pushes back against an object.
Tension definition
The force in a string or other flexible one-dimensional object that is caused by the force applied to its ends.
Frictional force definition
The force due to the interaction of an object and the surface it sits on. Affected by surface roughness and chemical reactions between surfaces.
Maximum frictional force
Ffric = μN
Maximum frictional force (Ffric) is the point where the force of friction can no longer balance applied force. (Newtons)
Coefficient of friction (μ) is a value which depends on the properties of both object and surface. (No units)
N Is the size of the normal reaction force between the object and surface. (Newtons)
Normal reaction/weight equation
N = mg
Normal reaction (or weight) = mass x gravity
What’s a component?
The part of a force that acts in a given direction, parallel to a given axis.
Resolving forces
The process of identifying the components of a force that are parallel and perpendicular to a given direction
Acceleration definition
This is the rate of change in velocity measured in m/s/s. It has a magnitude and direction associated with it like velocity.
Acceleration equation
Average acceleration= ( change in speed (final speed-initial speed)) / time taken to change speed.
A = (v-u) / t
Newtons second law of motion equation
The total force applied to an object is equal to the mass of the object times the acceleration.
Applied force = mass x acceleration
F = ma
The acceleration is in the same direction as the force.
Newtons third law
Every action has an equal and opposite reaction.
Electric charge definition
A fundamental property of matter. There are two types of charge, positive and negative. Like charges repel and unlike charges attract.
If matter has an equal number of positive and negative charge particles then it is said to be electronically neutral.
Charge is measured in coulomb (C).
Electric force definition
The force produced on a charged object by another electric charge. The electric force between the two objects depends on Coulomb’s law.
Coulomb’s law
Describes the electric force between 2 objects.
F el = ke ((Q1 Q2)/r^2)
Q1 and Q2 represent the value of the two charges and r to represent the distance between them.
ke is a constant with a value of 8.99 x10^9 N m^2 C^-2
Electric field definition
The region where electronic forces act, produced by a stationary electric charge or by a varying magnetic field.
Calculate electric force using an electric field
Electric force can also he calculated with the equation.
F el = Qε
Where F el is electric force, Q is the charge of an object and ε is the strength of the electric field.
