-7 is correct because a negative plus a negative is always a negative
For this case, the first thing we are going to do is write the generic equation of motion for the vertical axis.
We have then:
Where,
- <em>g: acceleration of gravity
</em>
- <em>vo: initial speed
</em>
- <em>h0: initial height
</em>
For the first body:
For the second body:
By the time both bodies have the same height we have:
Rewriting we have:
Clearing time:
Answer:
it takes 18.31s for the two window washers to reach the same height
One side of the square measures 28 inches. Use 3.14 for π.
52. Rahzel wants to determine how much gasoline they had every month
=> He used 78 1/3 gallons of gas monthly
=> his wife used 41 3/8 gallons of gas last month
How much is to total of gas that they both used.
First let’s convert this fraction to decimal
=> 78 1/3 = 78.33
=> 41 3/8 = 41.38
Now, let’s start adding.
=> 78.33 + 41.38 = 119.71 this is already rounded to the nearest hundredths.
S = d/t
st = d
t = d/s
The time going is t1.
The time returning is t2.
The total time is 4 hours, so we have t1 + t2 = 4
The speed of the current is c.
The speed going is 9 + c.
The speed returning is 9 - c.
t1 = 16/(9 + c)
t2 = 16/(9 - c)
t1 + t2 = 16/(9 + c) + 16/(9 - c)
4 = 16/(9 - c) + 16/(9 + c)
1 = 4/(9 - c) + 4/(9 + c)
(9 + c)(9 - c) = 4(9 - c) + 4(9 + c)
81 - c^2 = 36 - 4c + 36 + 4c
81 - c^2 = 72
c^2 = 9
c^2 - 9 = 0
(c + 3)(c - 3) = 0
c + 3 = 0 or c - 3 = 0
c = -3 or c = 3
We discard the negative answer, and we get c = 3.
The speed of the current is 3 mph.
