Makin’ Bank: Straight Line Motion Practice Quest

Do all numerical problems algebraically first, then plug in the numbers.

1. Using the following position vs time graph, fill in the table for v and a using +, -, or 0.

2. You are down on your luck and need to make some bank. You walk into a coffee bar and make the following offer to the barista behind the counter. “If you can catch this $20 bill before it falls through your fingers without dropping your hand, I’ll give you the bill. If you don’t catch it, you owe me twenty.” You hold the bill vertically as shown, so that the barista’s finger and thumb are on opposite sides of the bill, with her thumb right over Andrew Jackson’s face, a distance of 7.0 cm from the top of the bill.

x vs t

x

t A B C D E F G

Δx = 7.0 cm

A) What will the acceleration of the bill be, when you drop it? (Hint: it will be the same as a dropped rock!)

B) How quickly (time!) will the barista have to close her hand to catch the bill before it slips through her fingers?

C) A typical reaction time is 0.18 seconds. Does the barista stand a chance of catching your bill?

D) If you were somehow able to keep making money at this rate (when the bill is actually falling the 7.0 cm distance) for an entire hour, how much money would you earn?

1

AB BC CD DE EF FG

va

3. Clark and Jason are walking along in an old, abandoned mine when their flashlight goes out. They crawl ahead in complete darkness for a while, feeling their way along a tunnel when suddenly they come to a drop-off of unknown depth. What to do? Clark comes up with a plan. “I figured out a way to get the depth. It’s so obvious,” he says. “Don’t you see? Drop a rock from the edge; I’ll time its fall and calculate the depth.” Annoyed, Jason reluctantly agrees. He calls out when he releases the rock and Clark measures a time of 0.50 seconds when he hears the rock hit the top of a debris pile at the shaft’s bottom.

JasonClark

SHAFT

debris pile

A) How far down is the bottom (top of debris pile) according to Clark’s calculation?

B) Jason is really annoyed by Clark’s condescending tone, so instead of simply dropping the rock (as in part A), he secretly throws it with an initial velocity of 10 m/s, straight down. How deep is the actual drop-off (again, measured to the top of the debris pile)? Label the sketch at left with all the relevant variables.

C) Mislead by the calculation in part A) Clark jumps down the actual distance. How fast is he going when he impacts the top of the debris pile?

D) The debris brakes his fall, bringing him to rest over a distance of 0.50 m. What is his acceleration (assumed to be constant) in coming to rest? As part of your solution, do a new sketch, and label it.

2

4. You live in a really bad part of Redmond. While walking below a 10 story tenement building, someone drops a pipe bomb down on you from a window located 30.0 m above you. In order to survive, you can’t let the pipe bomb explode within 5.0 m of your person. After some very quick brainstorming, you reach down and pick up a discarded flower pot and heave it straight up with an initial speed of 14 m/s. As planned, the pot collides with the bomb 5.0 m above you, detonating it harmlessly. Sketch and label this!

A) How long does it take the pipe bomb to fall to within 5.0 m of you?

B) How long does it take the pot to reach the position 5.0 m above you from the instant you tossed it?

C) Using the information from A and B, how much time do you have to launch the pot upward from the instant the bomb was dropped? Would this have been enough time in real life?

5. What is the reading of this caliper in centimeters?3

4