Phys 1 Chapter 1, Exam 1

motion diagrams

series of images or visual depictions that describe or show a simplified view of motion

what is the differences between speed and velocity

velocity contains information about the direction of motion while speed does not

the quantity 2.67×10³ has how many sig figs?

3

the correct SI units for distance and mass are

meters, kilograms

if sam walk 100 m to the right, then 200 m to the left, his net displacement vector

points to the left

velocity vectors point

in the same direction as displacement vectors

the change of an objects position or orientation with time

motion

the path along which an object moves

trajectory

T or F: motion diagrams can show objects moving at constant speeds, speeding up, and slowing down and changing direction

T

models that describe properties in simplest terms possible

descriptive models

models with predictive power based on laws of physics

explanatory models

model where moving objects are treated as if all of its mass were concentrated at a single point

particle model

two runners jog along a track, the times at each position are show. which runner is faster?

both runners are moving at the same speed

the combination of an origin and axis marked in positive and negative directions

coordinate system

what is needed to specify a position

reference point (origin), distance from origin, and direction from the origin

the symbol that represents a position along an axis

coordinate

a change in position; the difference between a final position and initial position

displacement

Emily rides her bike on a country road that runs east-west past a water tower. Define a coordinate system so that increasing x means moving east. At noon, she is 3 miles east of the water town. a half hour later she is 2 mi west of the water tower . what is her displacement during that half hour?

1. make a drawing with a coordinate system with x increasing to the east.

2. find displacement: initial - final —> (-2 mi)=(3 mi) = -5 mi

Maria is at position x = 23m. she then undergoes displacement at deltax= -50 m. what is her final position?

-50=x-23 → -50+23 = -27; her final position is -27 m

an ant zig zags back and forth on a picnic table, the ants distance straveled and displacement are?

distance = 40, displacement = f-i = 10-40 = -30

motion at a constant speed in a straight line

uniform motion

speed formula

speed = distance traveled in a given time interval / time interval

velocity formula

v=displacement / time interval ; defined as the average velocity

Albatrosses are seabirds that spend most of their lives flying over the
ocean looking for food. With a stiff tailwind, an albatross can fly at high
speeds. Satellite data on one particularly speedy albatross showed it
60 miles east of its roost at 3:00 PM and then, at 3:15 PM, 80 miles
east of its roost. What was its velocity?

1. make line graph depicting the initial and final positions of the bird

2. use velocity formula: v = final - initial / time = 20 mi / 0.25 h = 80 mph

• the velocity is positive, which makes sense because the line graph shows motion to the right.

At t =12 s, frank is at x=25 m. 5 s later, hes at x = 20 m. what is franks velocity? (if it is to the left, it will be negative)

jenny runs 1 mi to the northeast, then 1 mi south. graphically find her net displacement

when measuring, certain precision is need. to do this, measurement if stated through —- —-:digits that are reliably known

significant figures

when multiplying or dividing, how do you know how many sig figs there should be?

based on the lowest number of sig figs in the problem

when adding or subtracting, the number of decimal places should be based on

the number with the least amount of decimal places in the problem

rank in order from most to least, the number of sig figs: a. 8200, b. 0.0052, c. 0.430, d. 4.321×10^-10

d > c > b = a

when a physical quantity is described by a single number

scalar quantity

quantity that has both a size and a direction

vector quantity

the size or length of a vector

magnitude

how is a vector graphically represented

with an arrow

vector that represents the distance and direction of an objects motion; it is drawn from the objects initial to its final position, regardless of the actual path followed between the two poins

displacement vector

Anna walks 90 m due east and then 50 m due north. what is her displacement from her starting point?

1. draw a right triangle with vectors and identify its sides

2. use soh cah toa to determine lengths

3. find the hypot. to find the net displacement

   1. use pythagorean theorem: d²net = (50m)²+(90)² → 103m

4. now use tan. to find the angle for the direction

   1. tan^-1 (50 m/90m)=tan^-1(5/9)=29 degrees

5. the net displacement if 100 m 29degree north east