5. Q: "A boat crosses a 2.85 km lake in 28 min. Find it's average velocity".(adsbygoogle = window.adsbygoogle || []).push({});

A: We want the answer in m/s, so I have to convert km to m, and min to s, right? Now I know how to do that, but not in the calculative way. I know that there is 1000 m in one km, so I multiplied 85 by 1000 and got 85 000 m. I know there is 60 s in one minute, so I multiplied 28 by 60 and got 1680 s. Then I divided 85 000 m / 1680 s and got50.60 m/s

6. "Johann walks north at 6.5 km/h for 32 min. He then runs south at 18.5 km/h for 3.0 min."

First of all, I should convert everything to m/s, shouldn't I? So 6.5 km/h = 1.81 m/s, 32 min = 1920 s. 18.5 km/h = 5.14m/s, and 3.0 min = 180 s.

a. Q: What is Johann's average speed?

A: Since speed is scalar, I don't have to worry about the direction. So speed=total distance/total time

I need to get the distance of the northern direction, so I go: d=vt = d= (1.81m/s)(1920s) = 3475.2m

Then I get the distance of the southern direction; d=vt = d= (5.1

4m/s)(180s) = 925.2 m

So the total distance travelled was 4400.4 m.

The total time was 2100 s.

So to get the total speed: = total distance/total time = 4400.4 m / 2100 s = 2.09733 m/s

=2.10 m/s(significant digits)

b. Q: Find Johann's average velocity.

A: Velocity is a vector, so you have to take direction into account. So when he goes north, the value of the distance is positive, and when he goes north the value is negative. So for total distance traveled to find the velocity I have to add both distances together: 3475.2m + (-925.2 m) = 2550 m.

And then I divide that by the total time (since time can never be negative):

2550m/2100 s =1.21 m/sIs that correct?

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# Homework Help: Constant velocity questions (average speed vs. average velocity)

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