Answer:

Explanation:
Given that
Train 1 (observer):
Speed = 109 km/h
Train 2 (source):
Speed = 99 km/h
Train 2 emitting frequency = 500 Hz
We know that observer and source are moving toward each other, then frequency heard by observer can be given as follows

Where C is the velocity of sound (C=1225 Km/h)
Now by putting the values



The answer of the problem is 56
Color is the least useful property for identification, as the same mineral type can be found in several different colors due to impurities in the mineral.
Condensation endothermic or exotérmica
Answer:
<h2>34.67 W</h2>
Explanation:
Power is the rate at which work is done and can be found by using the formula

p is the power in Watts (W)
w is the workdone in joules
t is time in s
but workdone = force × distance
From the question
force = 780 N
distance = 2 m
workdone = 780 × 2 = 1560 N
Since we now have the value of workdone we can find the power
We have

We have the final answer as
<h3>34.67 W</h3>
Hope this helps you