# 17 Unit 1 Review, Practice and Assessment

### Unit 2 Learer Objectives [Corresponding Example Course Outcome #]

- Find necessary conversion factors and convert between SI and non-standard units for several physical quantities. [1]
- Perform order of magnitude estimation. [2]
- Provide definitions for, and describe the connections among, distance, speed, position, displacement, velocity, and acceleration. [2]
- Apply basic kinematics to analyze the motion of objects and model experimental data [3].

**Outcome 1**

1) What is the height in meters of a person who is 6 ft 1.0 **in**. tall? (Assume that 1 meter = 39.37 **in**.)

2) The speed of sound is measured to be 342 **m/s** on a certain day. What is this in km/h?

3) Soccer fields vary in size. A large soccer field is 115 **m** long and 85 **m** wide. What are its dimensions in feet + inches? (Assume that 1 meter equals 3.281 feet.)

4) Tectonic plates are large segments of the Earth’s crust that move slowly. Suppose that one such plate has an average speed of 4.0 **cm**/year. (a) What distance does it move in 1 **s** at this speed? (b) What is its speed in kilometers per million years?

**Outcome 2**

5) Make an order of magnitude estimate of the number of cells in a hummingbird, assuming all the cells are the same size and approximating the the mass of an average cell to be ten times the mass of a bacterium. Be sure to cite your source for the size of a bacterium. (b) Making the same assumption, how many cells are there in a human?

(Exercises for outcomes 3 and 4 adapted from OpenStax College Physics ^{[1]}

**Outcome 3**

6) Explain the difference between distance and displacement.

7) Explain how velocity relates to position and how acceleration relates to velocity.

8) An object is thrown into the air and then caught. Assume the speed is slow enough that air resistance is negligible.

a) How much speed does the object lose each second on the way up?

b) What is the speed at the peak height?

c) How much speed does the object gain each second as it falls back down?

d) Are the starting and finishing speeds the same?

e) Are the starting and finishing velocities the same?

**Outcome 4**

9) A toddler runs away from a parent at 0.3 **m/s** for 3 **s**, stops for 2 **s** to see if they are being chased.

a) Draw a velocity vs. time graph for the toddler’s motion

b) Draw an acceleration vs. time graph for the toddler’s motion

c) Draw a position vs. time graph for the toddler’s motion (you will need to calculate the displacements that occur during each interval in order to draw this graph).

10) Upon realizing they might be chased after the 2 **s** stop, the toddler from the previous exercise begins slowly walking away and increasing speed into a run, reaching a speed of 0.4 **m/s** only 3 **s** later.

a) Complete the acceleration vs. time graph for the toddler’s motion, now including this new motion. You may draw a new graph or add to your previous graph in a different color. (You will need to calculate the acceleration during this last part of the toddler’s motion in order to complete this graph).

b) Complete the velocity vs. time graph for the toddler’s motion. You may draw a new graph or add to your previous graph in a different color. (You will need to use the acceleration you found above to calculate a change in velocity to complete this graph).

c) Complete the position vs. time graph for the toddler’s motion. You may draw a new graph or add to your previous graph in a different color. (You will need to use the acceleration you found above to calculate displacements to complete this graph).

11) Describe the motion depicted by the following velocity vs. time graph. The vertical axis tick marks indicate 1 **m/s** intervals, starting from zero **m/s** at the horizontal axis.

12) Draw the acceleration vs. time graph associated with the velocity vs time graph above.

13) Draw the position vs. time graph associated with the previous velocity and acceleration vs. time graphs.

- OpenStax, College Physics. OpenStax CNX. Jul 16, 2018 http://cnx.org/contents/031da8d3-b525-429c-80cf-6c8ed997733a@11.35. ↵
- Velocity Graph Uploaded by Riaan at English Wikibooks and transferred from en.wikibooks to Commons., GFDL, is licensed under CC BY-NC-SA 4.0 ↵