Suzie (of mass 70 kg) is roller-blading down
the sidewalk going 20 miles per hour. She
notices a group of workers down the walkway
who have unexpectedly blocked her path, and
she makes a quick stop in 2.2 seconds.
What is Suzie’s average acceleration?
1. -34.2657
2. -3.43803
3. -4.46944
4. -1.98642
5. -134.083
6. -15.8914
7. -4.06313
8. -5.84466
9. -7.44907
10. -62.5722
Answer in units of m/s
2
(-20mi/hr)/2.2s * 1609m/mi * 1hr/3600s
= (-20*1609)/(2.2*3600) m/s^2
Vo = 20mi/h * 1600m/mi * 1h/3600s = 8.9 m/s.
V = Vo + a*T = 0,
8.9 + a*2.2 = 0,
a = -4.04 m/s^2.
To find Suzie's average acceleration, we need to use the formula:
average acceleration = change in velocity / time
First, we need to convert the velocity from miles per hour to meters per second. We know that 1 mile is equal to 1609.34 meters, and 1 hour is equal to 3600 seconds. So:
20 miles/hour = (20 * 1609.34) / 3600 = 8.9392 m/s
Next, we need to calculate the change in velocity. Since Suzie is stopping, her final velocity will be 0 m/s. We can calculate the change in velocity as:
change in velocity = final velocity - initial velocity
= 0 - 8.9392
= -8.9392 m/s
Finally, we can calculate the average acceleration using the given time of 2.2 seconds:
average acceleration = change in velocity / time
= -8.9392 / 2.2
≈ -4.06313 m/s²
Therefore, the answer is option 7: -4.06313.
To find Suzie's average acceleration, we can use the equation:
acceleration = (final velocity - initial velocity) / time
First, we need to convert Suzie's speed from miles per hour to meters per second. We know that 1 mile is equal to 1609.34 meters, and 1 hour is equal to 3600 seconds.
So, Suzie's initial velocity would be:
initial velocity = 20 miles/hour * (1609.34 meters/mile) / (3600 seconds/hour)
initial velocity = 8.9408 m/s
Now, we need to find Suzie's final velocity. She comes to a stop, so her final velocity is 0 m/s.
Finally, we know that the time it takes for Suzie to stop is given as 2.2 seconds.
Now we can substitute these values into the equation to find the average acceleration:
acceleration = (0 m/s - 8.9408 m/s) / 2.2 s
acceleration = -8.9408 m/s / 2.2 s
acceleration = -4.0631 m/s (rounded to four decimal places)
Therefore, the correct answer is option 7: -4.06313 m/s.