Example Problem 1 for Average Velocity

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Study Guide for Physics Test over one dimensional motion
First you need to know the answer to the following question:
What is the definition of Physics that Mr. Strawn prefers?
Physics is the study of matter and energy and the interactions that occur between them.
Second, you need to know the S.I. prefixes from Giga (G) to nano
(n). You need to know the
number associated with each prefix.
Example Problem 1 for Average Velocity
A car drives along the highway at 115 km/h for 2.50 h. Once in the city, the car drives at 60.0
km/h for the next 0.500 h. Determine the average velocity of the car.
The average velocity is based on the total displacement of the car for the entire time it was moving, so
we first need to figure out the total displacement and the total time.
First part of the drive...
Second part of the drive...
So, in total, the car moved 317.5 km in 3.00 h. Its average velocity is...
Practice problem 1 for Average Velocity
An automobile travels on a straight road for 40 km at 30 km/h. It then continues in the same direction
for another 40km at 60km/h. What is the average velocity of the car during this 80 km trip?
Example Problem 2 for Constant Acceleration
A bus that is traveling at 30.0 km/h speeds up at a constant rate of 3.5 m/s2. What velocity
does it reach 6.8 s later?
Example Problem 3 for Constant Acceleration
A car slows from 22 m/s to 3.0 m/s at a constant rate of 2.1 m/s2. How many seconds are required
before the car is traveling at 3.0 m/s?
Example Practice Problem 2
An airplane accelerated uniformly from rest at the rate of 5.0 m/s2 for 14 s. What final velocity did it
attain?
Answer = 7.0 x 101 m/s
Example Problem 4
A car moving westward along a straight, level road increases its velocity uniformly from +16 m/s
to +32 m/s in 10.0 s.
a. What is the car’s acceleration?
b. What is its average velocity?
c. How far did it move while accelerating?
Practice Problem 3
A snowmobile has an initial velocity of +3.0 m/s..
a. If it accelerates at the rate of +0.50 m/s2 for7.0 s, what is the final velocity?
Answer = 6.5 m/s
c. If it accelerates at the rate of −0.60 m/s2, how long will it take to
reach a complete stop?
Answer 5.0 seconds
Example Problem 5
A car accelerates from rest at −3.00 m/s2.
a. What is the velocity at the end of 5.0 s?
b. What is the displacement after 5.0 s?
Free Fall Problems
Example Problem 6
A ball is thrown vertically upward with the speed of 25.0 m/s from a height of 2.0 m.
a. How long does it take to reach its highest point?
b. How long does the ball take to hit the ground after it reaches its
highest point?
Practice Problems 4
A tennis ball is thrown straight up with an initial speed of 22.5 m/s. It is caught
at the same distance above the ground.
How high does the ball rise?
Answer = 25.8 meters
How long does the ball remain in the air? Hint: The time it takes the ball to rise
equals the time it takes to fall.
Answer = 4.60 seconds
Study your Graphing Flash Cards and Know what the different shapes on the three
different graphs mean.
Position verses Time Graphs, Velocity verses Time Graphs, and
Acceleration verses Time Graphs
Illustration 1: d-t graph of a person running a marathon.
From Zero to 90s
Look at how you are running in those first 90 seconds.
Every 30 seconds you have moved about another
150m away from the starting point… you must be
moving at a constant positive velocity!
A constant positive velocity is shown on a d-t graph
as a straight line that slopes upwards. It is a linear
relationship.
From 90s to 150s
Yikes! You ran too fast at the start and now you’re out of
breath!
During this time period, your position on the graph
has stayed the same…450m.
This just means that you are standing in the same
spot, exactly 450m away from where you started.
A flat horizontal line means you are stopped.
From 150s to 240s
You must have started running forward again, since a positively sloped line means a positive
velocity. Notice that this section of line is a little steeper than the first section. You are now
running about 200m every 30s. A steeper line (which has a bigger slope) means that you are
moving at a faster constant velocity.
From 240s to 300s
In this section the line slopes down, which means it has a negative slope.
Since slope is equal to velocity, this must mean that you are running backwards.
A negative slope means a constant negative velocity.
You must have forgotten to pass a check point, so you ran back to it.
From 300s to 360s
Again, we have a horizontal line. You must be stopped.
From 360s to 510s
You know that you have only one chance to still win the race… run as fast as you can!
During this time period, the line curves upwards.
The line becomes steeper and steeper as it continues. This means that the slope of the line is
getting bigger and bigger.
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