Exam 1 Flashcards
Precision vs Accuracy
Precision- Getting the same answer over and over
Accuracy- Getting close to the right answer
km
m
cm
mm
What are the units for common physics problems
Distance
Velocity
time
acceleration
Distance- length is meter
Velocity- meter/ second
time- second
acceleration- m/s^2
What is the rule of thumb about units/dimensions?
need to be dimensionally consistent. i.e units on the left of the equal sign must match the left over units on the right side. (Units must cancel to be equal)
Unit conversions giga-pico
Distance
Total length traveled. Always positive. most often need to convert to Meters
Displacement
Change in position. Can be positive or negative to give direction
Average speed
avg speed=distance/elapsed time
Always positive as distance and time are always positive.
SI units are meters/second, or m/s
Average velocity
v.avg=displacement/time
change in x/change in t
where displacement is x.f - x.i
not always positive since displacement is directional
SI units are meters/second, or m/s
Slope is equal to _______________
Slope is equal to the average velocity
therefore a negative slope means a negative velocity, moving backwards or to the left
change in x/change in t
Instantaneous Velocity
This idea of a velocity corresponding to an instant of time
When the velocity is constant, the ________ velocity over any time interval is
equal to the __________ velocity at any time.
When the velocity is constant, the average velocity over any time interval is
equal to the instantaneous velocity at any time.
The instantaneous velocity at a given time is equal to the _______ of the ____________ at that point on an x-versus-t graph.
The instantaneous velocity at a given time is equal to the slope of the tangent line at that point on an x-versus-t graph.
Acceleration
Average Acceleration
Rate of change of velocity with time.
Meters per second per second m/s/s
equation for average velocity
Vavg= displacement/time
V= (Xf-Xi)/(Tf-Ti)
equation for average speed
= distance/time
When is instantaneous velocity equal to average velocity?
When the graph is a linear line. x vs t is linear progression
An elevator is moving downward when the emergency button is pressed and comes to a stop a short time later.
After the button has been pressed but before it stops, the velocity of the elevator is _________ and the acceleration is ________
After the button has been pressed but before it stops, the velocity of the elevator is negative and the acceleration is positive
A child throws a ball upward.
Immediately after the ball leaves the child’s hand, the velocity of the ball is ________ and the acceleration of the ball is _________
At the very top of the balls motion (maximum height) the velocity is _______ and the acceleration is ________
Immediately after the ball leaves the child’s hand, the velocity of the ball is positive and the acceleration of the ball is Negative
At the very top of the balls motion (maximum height) the velocity is zero and the acceleration is negative
What is a vector
A vector is a mathematical quantity with both a magnitude and a direction
What is a scalar
A scalar is a number with units. It can be positive, negative, or zero
What is meant by magnitude?
Distance covered
What is the slope equal to on an x vs t graph?
velocity- change in x / change in t
What is the slope equal to on a v vs t graph?
acceleration- change in v / change in t
What information can you gain from a v vs t graph?
The slope is equal to acceleration (V/t)
The area under the curve is equal to displacement.
Acceleration v time graph
Magnitude of a Vector
Find the x and y component of a vector
x comp= Mag cos( degree)
y comp= mag sin (degree)
Find the direction angle of a Vector
tan-1(y comp/x comp)
