Question

roduction to motion
on july 30, 2016, aikins jumped from an aircraft without any parachute or wingsuit at an altitude of 25,000 feet (7,620 m) above simi valley, california, watched by a live audience.
after about two minutes of free fall he successfully landed in a 100-by-100-foot (30 by 30 m) net just outside of simi valley, california.
key questions
how far did luke aikins fall? (in meters)
how much time did it take him to fall this distance? (in seconds)
how can we calculate his average speed?

the average speed of an object is defined as:
→ the total __________ traveled divided by the amount of __________ it took to travel that distance.

$v = $
$d = $
$t = $

• in physics, we use ________ units; international system of metric measurements
• when distances are measured in meters and time is measured in seconds, the standard unit of speed is ________
• this is different from what we are used to ________

question: what is lukes average speed?
given:
$v = $
$d = $
$t = $
formula:
$v = \frac{d}{t}$
solve:

Explanation:

Step1: Find fall distance (meters)

From text: $d=7620$ m

Step2: Convert fall time to seconds

$t=2\text{ minutes}=2\times60=120$ s

Step3: Recall average speed definition

Average speed = $\frac{\text{total distance}}{\text{total time}}$

Step4: Fill definition blanks

First blank: distance; Second blank: time

Step5: Derive speed-related formulas

From $v=\frac{d}{t}$:
$d=v\times t$, $t=\frac{d}{v}$

Step6: Fill physics unit blanks

1. SI (metric) units; 2. m/s; 3. mph (imperial speed unit)

Step7: Calculate average speed

Substitute values: $v=\frac{7620}{120}=63.5$ m/s

Answer:

1. 7620 meters
2. 120 seconds
3. Average speed = total distance / total time
4. distance; time
5. $v=\frac{d}{t}$; $d=v\times t$; $t=\frac{d}{v}$
6. SI; meters per second (m/s); miles per hour (mph)
7. 63.5 m/s