Unit 2: 1-D MotionTEST REVIEW

Due Thursday,Sept 8 (middle of class). Test on Friday, Sept 9.

1)What are some examples of displacement units?

mmikm

2)What are examples of velocity units?

m/smi/hrkm/hr

3)What are examples of acceleration units?

m/s2mi/hr2km/hr2

4) Equations reviewed:

Average Velocity:
or / rearrange for Δx:


/ rearrange for Δt:

Acceleration:
or / rearrange for Δt:

Displacement:
or

5) Identify variables and units using meters and seconds:

In words: / Units: / In words: / Units:
ti / Initial time / s / vi / Initial velocity / m/s
tf / Final time / s / vf / Final velocity / m/s
Δt / Change in time / s / Δv / change in velocity / m/s
xi or di / Initial position / m / vavg / Average velocity / m/s
xf or df / Final position / m / a / Acceleration / m/s2
Δx or Δd / Displacement or
change in position / m

6)Slope of a Distance vs Time graph represents __VELOCITY______.

Slope of a Velocity vs Time graph represents __acceleration______.

7)What is a Vector?Example of vector:

Quantity with magnitudeDisplacement, velocity, acceleration

and direction

What is a Scalar?Example of scalar:

Quantity with magnitude ONLY,distance, speed, time

no direction

8)Below is a graph of a runneron a course. Identify the following.

  1. What is his displacement after 4 sec?

X4 = Position at 4 sec is 5m

X0 =Posistion at 0 sec is 0 m

Displacement:

  1. When did the greatest velocity occur?

Steepest slope is fastest which occurs from 0 to 2 sec and velocity is (5-0)/(2-0) = 2.5 m/s

  1. What was the average speed from 8 to 10 sec?

= 1.5 m/s

  1. What is the acceleration from 4 to 6 sec?

On a position vs time graph, a straight slope means a constant velocity, therefore there is no acceleration (means a CHANGE in velocity over time)

  1. Did the runner return to its starting position? If yes, when?

Yes, at 8 sec the runner changed directions at 8 sec.

9)Below is a graph of a different car on the road. Identify the following.

  1. What is its displacement after 4 sec?

Displacement can be found several ways –

find acceleration (slope) and use

Or use which rearranges to:

So displacement is 8m.

  1. When did the greatest velocity occur?

On this velocity vs time graph, the largest magnitude is 4m/s, so greatest velocity occurred at a constant rate from 4-6 sec.

  1. What was the average speed from 4 to 6 sec?

4 m/s (constant during this time period). Else average the final and initial velocity.

  1. What is the acceleration from 8 to 10 sec?

On this velocity vs time graph, the slope is acceleration, so calculate slope from 8 to 10 sec.

= -2 m/s2

  1. Did the car return to its starting position?You would have to calculate displacement for each section or use area under curve. But we are going to use logic without calculating. As the car is going a positive velocity for 90% of the time and only going in a negative direction or back- tracking for last half a second, the answer is NO.

10)Below is a graph of a cyclist’s motion on the road. Identify the following.

a)Describe the cyclist’s motion.

The cyclist has CONSTANT POSITIVE ACCELERATION

b)Identify for time interval from 0 to 6 sec?

c)What was the displacement after 6 sec?use givens above

= (0m/s) (6s) + ½ (4m/s2)(6s)2 = 72m

d)What was the velocity after 6 sec?

e)What is the acceleration from 8 to 10 sec?

Constant the whole time, so still 4 m/s2

11)Use diagram to answer a, b, and c.

a)How far did I walk if I travelled Path A? (from pt1 to pt2)

15 m

b)What is displacement from Pt 1 to Pt2?

Displacement is shortest distance between two points – 12m

c)If it took 10 sec to get from Pt 1 to Pt 2, what was my velocity?

= 1.2 m/s

12)If I traveled 12 m East, then 5 m West, what is my displacement?

East is positive and West is negative. So, +12m – 5 m = 7 m, East

13)Draw the Distance vs Time, Velocity vs Time, and Acceleration vs time for an OBJECT AT REST. List three real world examples.

Real World Examples:


14)Draw the Distance vs Time, Velocity vs Time, and Acceleration vs time for an OBJECT MOVING IN A NEGATIVE DIRECTION AT CONSTANT RATE. List three real world examples.

Real World Examples:

15)Draw the Distance vs Time, Velocity vs Time, and Acceleration vs time for an OBJECT DECCELERATING IN A POSITIVE DIRECTION. List three real world examples.

Real World Examples:

16)Draw the Distance vs Time, Velocity vs Time, and Acceleration vs time for an OBJECT being dropped. List three real world examples.

Real World Examples:

17)On the position Time Graph, Two individuals motion is shown, A and D. Answer the following questions:

a)Which object had the fastest speed?

Steepest slope A

b)Which object was travelling backward?

Negative slope, D

c)What is occurring at 1 sec (the intersection)?

Both objects are at same position.

17) Describe what type of motion is occurring in each graph at each second:

What type of graph is this?
Position vs TiME / What type of graph is this?
Velocity vs TiME
Section / Describe motion / Section / Describe motion
A / At rest / F / Accelerating in a negative direction
B / Decelerating in a positive direction / G / Accelerating in a positive direction
C / Constant fast negative velocity / H / Constant velocity
D / Constant slow negative velocity / J / Slowing down or deceleratin
K / At rest

18)A crosscountry runner crosses the finish line running at 4 m/s. He takes 2 seconds to stop after crossing the line.

  1. What is his acceleration?

He is slowing down.

  1. How far did he travel?Use same givens as above.

19)A mouse is sitting in a corner. The cat approaches and the mouse takes off at an acceleration rate of 50cm/s2. He is 2 meters from his hole.

  1. How long does it take him to get home?
  1. What speed was he going when he got to his hole?

20)Vocabulary in Questions. Identify if initial, final or change in position, velocity, acceleration, or time equal to a specific value.

  1. If an object is “released”, what variable is equal to what?
  2. Ex: A ball is released to roll down a ramp for 4 ft and reaches the bottom rolling 10 m/s.

Vi = 0

  1. If an object is “starting from rest” or “at rest”?
  2. Ex: The runner started from rest and traveled 5 m in 4 seconds.

Vi = 0

  1. If an object is “coming to a stop”?
  2. Ex: After traveling at 30 mi/hr, the car came to a stop in 3 seconds.

Vf = 0