P1 Flashcards
What are rulers used to measure?
Small distances-centimeters, to the nearest millimeter
How are larger distances measured?
Tape measure or trundle wheel
How are volumes of liquids measured?
Using measuring cylinders
How is the volume of irregular shapes measured using measuring cylinders?
By measuring the change in volume (v=measure before-measure after)
What are the two scales on a micrometer screw gauge called and where are they located? How much can they each measure?
Main scale- located on shaft, measures to the nearest O.5 mm
Fractional/thimble scale- rotating barrel, 59 division totaling to O.5 mm
How do you use a micrometer screw gauge?
Turn the barrel until the jaws tighten
Use friction clutch to ensure correct pressure
Read main scale to nearest 0.5mm
Read additional fractional scale of a mm
Add together
What is an important factor to consider when measuring time intervals?
Human reaction time
How can human reaction speed be combated when measuring intervals?
By measuring multiple small intervals as one big one, then dividing the total time by the amount of small intervals
Define speed
Speed is the measure of how far an objects move in a given time. (DOES NOT depend on direction)
What is the equation for speed (with distance and time)?
Speed=distance/time
Define velocity (and positive and negative velocity)
Velocity is the speed and the direction in which an object is moving
Positive-away from starting point
Negative-towards starting point
!think starting point is 0!
What is the equation for acceleration? What is its unit of measurement?
Acceleration= change in velocity (final-inital)/time
Acceleration -> m/s^2
What does the gradient of a distance-time graph represent?
What does a curved, straight and no slope mean?
Gradient -> speed
Curved slope -> non uniformed speed
Straight slope -> uniform speed
No slope -> stationary
What does the gradient and area of a speed-time graph represent?
What does it mean when the gradient is:
A straight line at the bottom
Straight line
Straight diagonal line
Curved line
Gradient -> acceleration
Area -> distance
Straight line at bottom -> at rest
Straight line -> constant speed
Straight diagonal -> constant acceleration
Curved line -> changing acceleration
What does a falling object accelerating imply?
A force is acting upon it, pulling it down
What is the unit g? What is the logic behind the unit?
Gravitational force per unit mass (10n/kg -> g)
Weight (force of gravity on mass)-> newtons
Earths gravity -> 10N
1kg mass -> 10N
Is acceleration constant near to the earth?
Yes
All objects acceleration at the same rate near the earth and in space (10 m/s^2)
What is mass?
The amount of matter an object is made of (kg)
What is weight?
The gravitational force upon an object
Weight=mass x gravitational force per unit (g)
What is a source of gravitational field (the main really big one)?
The Earth
Define density (including low and high density and its implications on its mass)
Mass per unit volume of a material
Low density -> typically low mass
High density -> typically high mass
What is the equation for density?
Density=mass/volume
How would you find the density of a regularly shaped solid and a liquid?
Soild -> find mass then volume -> use formula
Liquid -> mass of beaker - mass of whole = mass of liquid -> find volume (ml=cm^3) -> use formula
How would you find the density of an irregularly shaped solid?
Mass using scale -> volume via displacement (water to predetermined level -> record level -> add object -> record new level -> subtract second from first -> use formula
How do unbalanced forces affect the acceleration of an object? How does mass affect acceleration?
Unbalanced forces -> accelerates in direction of resultant (basically the bigger)
Mass -> more mass, lower acceleration (f=m x a (force always the same))
Extension-load graphs - draw and label
- Extension proportional to force (straight line), object will return to original shape (elastic)
- Elastic limit (graph begin to curve)
- Extension not proportional to force, object will not return to original shape (not elastic)
- Breakage (vertical line)
What is hooke’s law?
The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality
As more force applied, greater the extension
What is the equation for Hooke’s law?
F=Kx
F (force in N) is directly proportional to x (extension in m)
K (spring constant (stiffness of material), equal to n/m)
What is the limit of proportionality for a extension load graph?
Limit of proportionality- where if more force is added, the extended object will not return to its original position when force is removed
Inelastically deformed
What is elastic limit?
When a material no longer shows elastic properties (doesn’t return to original size when force removed)
Material is permanently damaged (material is longer/larger than originally)
Material is weaker (above effect cause fractures of atomic bonds)
What is friction? What is an example?
A resistive force (slows things down) between two surfaces which impedes motion and always acts in the opposite direction of the object
Creates heats and wears down surfaces
Ex: air resistance
How do you find the resultant force?
Add all forces going in the same direction
Take away forces going in opposite direction
Remaining force -> resultant force
What happens to objects with no resultant force?
They remain at rest or at a constant speed
(Newtons first law - objects will stay ay rest or in constant motion until an unbalanced force acts upon it (ex: acceleration))
Give an example of rotation as a result of force
From one side of a pivot (fixed point object can rotates around)
Turning a bolt using a wrench
Define moment (force causing rotation)
The turning effect of a force about a pivot
How do you calculate the moment?
M= F x d
Size of moment=force x perpendicular distance from pivot (distance from pivot to the end of the object used to rotate)
M=Nm (newton meters)
F=N (newtons)
d=m (meters)
What does it mean when a system is in equilibrium?
No resultant force or resultant turning effect
If in motion, in constant motion (moving in a straight line or turning)
If stationary, stays stationary
What is the biggest moment called?
Defining moment
What is center of mass?
The point at which the weight of the object acts
How can you find the position of the center of mass of planes (2D)?
Uniformed, symmetrical shapes - center of gravity is at point of symmetry
Irregular shape
Center of gravity always along pivoting point
Object is suspended from point 1 (near edge, plumb line)
Line drawing directly down
Repeat from point 2 and 3
Crossing point is center of mass
How does the center of mass relate to stability of an object?
The object is stable when the center of gravity is directly above the base of the object
Line of action (line that shows tilt (from point at which it is tiliting)) needs to pass center of mass to lose stability
What are some factors that affect the position of the center of mass?
Wider base - lower center of gravity
Narrower base - high center of gravity (more likely to fall)
Bottom heavy - lower center of gravity
Top heavy - higher center of gravity
Define pressure
The concentration of a force or force per unit area
What is the equation for pressure?
Pressure= force/area
Area-always the area where the force is at a right angle
Example of pressure
Tractor - big wheels distribues force over a larger area, and reduces the pressure
Nail - sharp end concentrates the force over a smaller area, and increases the pressure
