AP Physics Unit 1

motion

any change in position of an object with respect to a frame of reference

frame of reference

a coordinate system based on one point in space and time

speed

the rate at which an object covers a distance or moves through space

velocity

the speed of an object in a specific direction

acceleration

the rate at which an object changes its velocity

scalar quantities

values that are fully described by magnitude (with numerical values) alone; direction is not important

vector quantities

values that are fully described by magnitude and direction

scalar (does not need direction

mass =

vector (needs direction: where or which way force is applied)

force =

scalar (total ground covered)

distance (meters) =

vector (final position-initial position)

displacement =

scalar (distance/time)

speed (m/s) =

vector (displacement/time)

velocity (m/s) =

vector (it measures rate of change in velocity, which involves direction)

acceleration =

scalar quantity

a quantity that is ignorant of direction is referred to as a

vector quantity

a quantity that is conscious of direction is referred to as a

True

True or False: an object can be moving for 10 seconds and still have zero displacement

distance traveled = 6 miles and displacement = 0 miles

You run from your house to a friend’s house that is 3 miles away. You then walk home. What is the distance you traveled and what was the displacement for the entire trip?

to include direction (like north, east, south, west)

when answering displacement questions, remember

distance/time

speed equation

250 mi/65 mi/hr = 3.8 hours

How long will it take you to travel 250 mi when traveling on a highway with a speed limit of 65 mi/hr?

v=d/t + direction or v=delta D/t (displacement/time)

velocity equation

displacement= 2 miles east, so 2 miles/1 hr = 2 mi/hr west

What is the velocity of an object that travels 5 miles west then 3 miles east then comes to rest in 1 hour?

speed is a quantity that describes how fast or slow an object is moving, while velocity is a quantity that is defined as the rate at which an object’s position changes

speed vs velocity

True (velocity depends on displacement, not distance; if you end at the same spot as you started moving, you have zero displacement)

True or False: it is possible for an object to move for 10 seconds at a high speed and end up with an average velocity of zero

B<C<A

Suppose that you run for 10 seconds along three different paths. Rank the three paths from the lowest average speed to the greatest average speed

A<B=C

Suppose that you run for 10 seconds along three different paths. Rank the three paths from the lowest average velocity to the greatest average velocity

avg speed= 4mi/hr and avg velocity= 0 mi/hr

You run from your house to a friend's house that is 3 miles away in 30 minutes. You then immediately walk home, taking 1 hour on your return trip.1- What was the average speed (in mi/hr) for the entire trip?2- What was the average velocity (in mi/hr) for the entire trip?

gas pedal, brake pedal, steering wheel

Accelerating objects are objects that are changing their velocity. What are the three controls on an automobile that cause it to accelerate.

(Vf-Vo)/t or change in velocity over time

acceleration equation

concave up

bowl that can hold water without spilling

concave down

a frown or a bowl that can’t hold water without spilling

with changing speed, in a circle, with any change in velocity

NOT when it is moving extremely fast or with constant velocity

An object is accelerating if it is moving:

maintaining a constant velocity

If an object is NOT accelerating, then one knows for sure that it is

change its velocity by 10 m/s in 1 s

an object with an acceleration of 10 m/s² will:

south direction of acceleration

a northbound car skids to a stop to avoid a reckless driver

upward direction of acceleration

an Olympic diver slows down after splashing into the water

velocity

position vs time graph slope =

positive velocity

position vs time graph positive slope =

negative velocity

position vs time graph negative slope =

changing velocity (which equals acceleration

position vs time graph changing slope =

constant velocity

position vs time graph constant slope =

negative acceleration

position vs time graph slope is concave down =

positive acceleration

position vs time graph slope is concave up =

acceleration

velocity vs time graph slope =

positive acceleration

velocity vs time graph positive slope =

zero acceleration (it means constant velocity, not standing still)

velocity vs time graph constant line (no change in slope) =

negative acceleration

velocity vs time graph negative slope =

changing acceleration

velocity vs time graph changing slope =

the displacement

area of the triangle under the line of the velocity vs time graph =

12,960 km/h²

to convert from m/s² to km/h² multiply by

3.6 km/h (3600/1000)

to convert from m/s to km/h multiply by

multiply by 1000m/1km and then by 1hr/3600 seconds

to convert from m/s to km/hr

standing still

a horizontal line on a position vs time graph means

constant velocity

a horizontal line on a velocity vs time graph means

constant velocity (zero acceleration)

what does a straight line that is increasing or decreasing mean on position vs time graph

there is a positive acceleration

what does a concave up (bowl holding cereal) slope of position vs time graph mean

there is a negative acceleration

what does a concave down (frown or upside down bowl) slope of position vs time graph mean

it means the object is slowing down (when velocity and acceleration have opposite signs; example: moving forward at a positive speed while accelerating backwards) (moving backward at positive speed while accelerating forwards is not negative acceleration since the acceleration is towards the positive direction)

what does negative acceleration mean

the object is moving backwards

what does a line below the x axis of a velocity vs time graph mean

the object is standing still

what does a line on the x axis of a velocity vs time graph mean