Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
37 Cards in this Set
- Front
- Back
dynamics is the study of_________, it is about the connection between_____ and ________. |
why objects move. Force and motion |
|
contact forces vs. force of gravity |
contact = object touching another object gravity = to touching |
|
Is force a vector or scalar? |
vector |
|
Newton's first law of motion: it is also called: It does not hold with: |
an object at rest tends to remain at rest. An object in motion tends to remain in motion the law of inertia certain reference frames |
|
inertia is: |
the tendency of an object to retain its state of rest or uniform velocity |
|
reference frames where Newton's first law holds are called: |
inertial reference frames (does not hold with non inertial reference frames) |
|
mass is a measure of: |
inertia. It will therefore require more force to stop and start objects with more mass (a truck vs. a baseball) |
|
mass vs. weight |
a property of matter vs. a force |
|
a net force causes... |
acceleration |
|
Newton's second law: |
The acceleration of an object is directly proportional to the net force actingon it, and is inversely proportional to the object’s mass. The direction of theacceleration is in the direction of the net force acting on the object. OR Net force = ma |
|
One newton |
the amount of force required to accelerate a l kg object at 1 m/s^2 --> Thus it equals kg * m/ s^2 |
|
SI = cgs = British = |
kg, N (kg*m/s^2) g, dyne (g*cm/s^2 slug, pound (lb) |
|
Conversion factors: 1 dyne = 1lb= slug= |
=10^-5 N = 4.45 N =14.6 kg |
|
Start: Chapter 6 work describes: equation: vector or scalar? |
what is accomplished when force acts on an object AND the object moves a distance W = Fd cos u, F=mag of constant force, d=mag of displacement, u= theta=angle between directions of displacement and force scalar |
|
Work unit: and it = |
joules (J) N*m |
|
Work unit cgs, and it equals Work unit British, and it equals |
erg, 1 dyne*cm foot pounds, ft*pounds 1 J=10^7 ergs=.7376 ft*lbs |
|
Can a force be exerted on an object and it do no work? Can there be displacement of an object and no work done on it? |
Yes - holding up a paper bag - there is no displacement, only force Yes, walking with a paper bag - there is no force in the direction of displacement on the bag |
|
It is important to specify whether you are calculating the work done ON an object of BY an object, as well as if you are calculating the work done by ONE particular for or the NET forces |
see other side |
|
Can work be negative? |
Yes, the work of a force can be negative when the object moves in the opposite direction of the force (e.g. friction will have a negative work) |
|
to estimate the work done by a varying force, you must graph it and then calculate the area underneath (FII vs. d) |
see other slide |
|
energy is defined as... |
the ability to do work |
|
kinetic energy= |
the energy of motion |
|
translation kinetic energy equation the work energy principle (words and equation) |
KE=1/2(m*v^2) the net work done on an object is equal to the change in an object's kinetic energy W(net)=change KE= 1/2mv2^2-1/2mv1^2 |
|
kinetic energy is measured in: |
joules/ ergs/ foot-pounds, JUST LIKE WORK |
|
Potential energy gravitational potential energy equation: change in potential gravity = |
energy associated with forces that depend on the position of an object relative to its surroundings PEg=mgy, where y=height above a ref level -Wg (the opposite of work done by gravity) |
|
Power |
the rate at which work is done, or the rate at which energy is transformed. |
|
Average power =______or_______ SI units British and horsepower |
work/time OR energy transformed/ time J/s or WATTS foot-pounds per second, 550 ft-lbs/ sec |
|
efficiency equation for power |
e=P(out)/P(in). Can never be > 1 because energy cannot be created |
|
Newton's 3rd law of motion |
whenever one object exerts a force on a second. The second object will exert an equal and opposite force back on the first |
|
uniform circular motion |
is said to happen when an object moves at a constant speed in a circle |
|
radial acceleration = centripital acceleration |
acceleration that is directed radially and towards the center of the circle, as in uniform circular motion |
|
Newton’s law of universal gravitation equation is called: |
states that every particle in the universe attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. the inverse square law |
|
radius of curvature |
when working with a partial circle, like a curve, this refers to radius. |
|
conservative forces vs. non-conservative forces |
work done depends only on the two positions and not the path taken. Non-conservative forces depend on the path taken. |
|
Law of conservation of energy |
energy can be transformed into one type or another, but the total energy remains constant |
|
when only conservative forces act... when non-conservative forces act |
the total mechanical energy is conserved (KE+PE = constant) Wnc = delta KE + delta PE |
|
dissapative forces |
reduce mechanical energy |