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Sauron [17]
3 years ago
8

A train travels 57 kilometers in 3 hours, and then 87 kilometers in 2 hours. What is its average speed? km/hr

Physics
1 answer:
skad [1K]3 years ago
3 0
Average speed (v) = total distance(d) / total time (t)
d = 57 + 87km = 144km
t = 2 + 3hrs = 5hrs
v = d÷t = 144÷5 = 28.8km/hr
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Two point charges, initially 3 cm apart, are moved to a distance of 1 cm apart. By what factor does the resulting electric force
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The answer is B (1/9).
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3 years ago
Excellent human jumpers can leap straight up to a height of
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For a human jumper to reach a height of 110 cm, the person will need to leave the ground at a speed of 4.65 m/s.  

We can calculate the initial speed to reach 110 cm of height with the following equation:

v_{f}^{2} = v_{i}^{2} - 2gh

Where:

v_{f}: is the final speed = 0 (at the maximum height of 110 cm)

v_{i}: is the initial speed =?

g: is the acceleration due to gravity = 9.81 m/s²

h: is the height = 110 cm = 1.10 m

Hence, the <u>initial velocity</u> is:

v_{i} = \sqrt{v_{f}^{2} + 2gh} = \sqrt{2*9.81 m/s^{2}*1.10 m} = 4.65 m/s

Therefore, the initial speed that the person must have to reach 110 cm is 4.65 m/s.

You can see another example here: brainly.com/question/13359681?referrer=searchResults

I hope it helps you!

4 0
2 years ago
A boat takes 3.0 hours to travel 50 km down a river, then 5.4 hours to return. Determine the speed of the water in the river.
Nutka1998 [239]

Answer:

3.7 km/h

Explanation:

Let's call v the proper speed of the boat and v' the speed of the water in the river.

When the boat travels in the direction of the current, the speed of the boat is:

v + v'

And it covers 50 km in 3 h, so we can write

v+v' = \frac{50 km}{3 h}=16.7 km/h (1)

When the boat travels in the opposite direction, the speed of the boat is

v - v'

And it covers 50 km in 5.4 h, so

v-v'=\frac{50 km}{5.4 h}=9.3 km/h (2)

So we have a system of two equations: by solving them simultaneously, we find the value of v and v':

v+v'=16.7 \\v-v'=9.3

Subtracting the second equation from the first one we get:

(v+v')-(v-v')=16.7-9.3\\2v'=7.4\\v'=3.7

So, the speed of the water is 3.7 km/h.


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The Celsius scale (^{\circ} C).

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