In a science lab, there is the adequate availability of raw materials for experiments such as chemicals while outside a science lab there isn't.
In a science lab, the availability of apparatuses and sources of heat is higher than outside a science lab.
<h3>What is science laboratory?</h3>
The science lab is a place where the experiments related to the science background are performed with the use of apparatus.
The science lab has plenty of equipment to perform the experiment whether related to physics or chemistry or biology.
Thus, source of heat and availability of raw material and equipment are the differences between the science activities carried out in a science laboratory and those carried out side of science laboratory.
Learn more about science laboratory.
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Answer:
1)
from the positive x-axis.
2) 
Explanation:
Given:
speed of rowing in still water, 
1)
speed of water stream, 
we know that the direction of resultant of the two vectors is given by:

where:
the angle of resultant vector from the positive x-axis.
angle between the given vectors
When the rower wants to reach at the opposite end then:

so,




from the positive x-axis.
2)
Now the resultant velocity of rowing in the stream:



Therefore time taken to cross a 4 miles wide river:



It's a plain, not a lever
Average speed=total distance traveled/time. Total distance=the sum of the two short distances=79*2+77*3=389 km. Total time used to travel is 2+3=5 hr. Average speed is 389/5=77.8 km/hr.