Mechanics Flashcards
v =
d/t
d =
v x t
t =
d/v
Distance-Time Graphs
- If the graph is a straight line then this shows that the object is moving at a constant speed
- Steeper the line, the faster the object is moving
- Horizontal the object is not moving (stationary)
- Gradient = rise/run
- Curved line the object is changing speed with accelerating or decelerating
Speed-Time Graphs
- A positive gradient shows the object is accelerating
- A negative gradient shows the object is decelerating
- If the line is horizontal the object is moving at a constant speed
- Gradient = rise/run = acceleration
- Distance = area of triangle = bxh/2
Mass (m)
The amount of matter in an object. It is in kilograms (kg). It does nor change when the object changes its position.
Weight (W)
The force of gravity acting on an object. It is measured in newtons (N). It may change if an object changes its position.
Support Force
When an object pushes down on a surface, the surface pushes back on the object. It always 90 degrees to the surface of the object is on.
Thrust Force
A push force, e.g from an engine.
Friction Force
A force that is always in the opposite direction to any motion.
Buoyancy Force
An upwards force from a fluid e.g water or air.
Lift Force
The upwards push on a wing (e.g an aircraft) due to its motion through air.
Tension Force
A pulling force e.g due to a rope or chain.
Weight Force
Due to gravity and it always acts straight down.
Weight =
mass x strength of gravity = mg
What is the strength of gravity on earth?
10 Nkg-1
Gravitational Fields
All objects are surrounded by force field. This field can be drawn as a series of lines with arrows;
- the direction of the gravity force (weight) that would act on a mass placed at that point
- the relative strength of the gravitational field - the close the field lines, the stronger the field.
Names of Gravitational Fields on Earth
Radial Field and Uniform Field
(earth from space) (surface of earth)
Balanced Forces
Means the object is at a constant speed
Unbalanced Forces
Means the object is accelerating/decelerating
When two arrows are the same direction
Total force = both arrows added up N
When two arrows are the opposite direction
Total force = difference between them
When an arrow is going up/down and one is going left/right
Total force = to find the hypotheses of a triangle (a2 +b2 = c2)
Newton’s Second Law
the net force on an object is proportional to the acceleration of the object;
F= ma
(if no given the force times the mass by 10)
Newton’s Third Law
for every action on one object there is an equal but opposite reaction on another object
Solid Friction
Is the force that opposes motion between the surfaces of two solid objects. The size of the solid friction;
-Depends on the smoothness of the two surfaces.
Fluid Resistance
Is created when an object moves through a fluid (liquid or gas). It is also called drag. If fluid is air, then the term air resistance is used.The size of the fluid resitance depends on;
- the speed of the object relative to the fluid
- the size and shape of the object
- the fluid used (its viscosity)
Terminal Velocity
The highest velocity attained by an object falling through a fluid. It is observed when the sum of drag force and buoyancy is equal to the downward gravity force acting on the object.
Energy
The capacity to do work which means you need energy for things to happen.
Kinetic Energy
Energy of a moving object (Ek)
e.g car, ball that is moving
Gravitational Potential Energy
Energy of an object due to its height above the ground (Ep)
e.g building, desk
Chemical Potential Energy
Energy stored in the chemical bonds of a substance
e.g batteries, petrol
Elastic Potential Energy
Energy stored in a stretched or compressed object
e.g rubber band, slinky
Sound Energy
e.g speaker, mouth
Light Energy
e.g sun, lightbulb
Heat Energy
e.f fire, sun
Electrical Energy
e.g charges, phones
Nuclear Energy
e.g bomb, nuclear power
Conversation Of Energy
Energy cannot be created no destroyed but instead is just converted from on form to another
Work
When a force moves an object for some distance in the direction of the force we say that work is done on the object by force. W = fd
The amount of energy gained or lost is equal to the amount of work done.
Power
Power is the rate of doing work. The faster something can do work, the more powerful it is. P = W/t
