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Question

11.Suppose you fire a rifle bullet (1630 m/s) in a shooting gallery and hear the gong on the target ring 0.725 s later. Taking the speed of sound to be 330 m/s and assuming the bullet travels straight downrange at a constant speed, how far away is the target?
m



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12. You jog at 6.0 mi/h for 5.0 mi, then you jump into a car and drive for another 5.0 mi. With what average speed must you drive if your average speed for the entire 10.0 miles is to be 10.8 mi/h?
mi/h

Answer 1

11.
Let x be the distance to the target, in meters.

The bullet takes x/1630 seconds to reach the target.
The sound of the gong takes x/330 seconds to get back to you.

You know that x/1630 + x/330 = 0.725

From there, just use algebra to solve for x.


12.
You want to travel 10 miles at 10.8 mph. The total amount of time required is 10/10.8 = 0.9259 hours.

If you jog five miles at 6.0 mph, the amount of time you spend jogging is 5/6 = 0.8333 hours.

Hence, you need to drive five miles in 0.0926 hours.

You can figure it out from there. :-)

Answer 2

No.11:
The speed of the bullet is immaterial to the first problem - only the time it takes for the sound to reach you is important.
The sound travels 330 m/s and how many meters will it travel in 0.725 seconds?
0.725(330)=239.25 meters

No.12:
The average speed for the first five miles is 6.

The average speed for the next five miles is X.

The average speed for the total 10 miles is 10.8

(6+X)/2=10.8
(6+X)=21.6
X=15.6 mph

Proof: 6 + 15.6 / 2 =
21.6/2=15.6 MPH

Answer 3

The bullet takes x/1630 seconds to reach the target.
The sound of the gong takes x/330 seconds to get back to you.

You know that x/1630 + x/330 = 0.725
From there, just use algebra to solve for x.

Answer 4

Do your OWN homework!
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