What are the answeres to these physics problems?

Question

I'm probably gonna do this ruetnely, (a good chance for me to vote you for best answers).

pls do give full work responses, so that I may learn.

1) Convert 1.90 km/h to m/s.

2) (a) How many square centimeters are there in 2 square feet? (1 in = 2.54 cm.)

(b) How many square centimeters are there in 2 square meters?

(c) Using your answers to parts (a) and (b), roughly how many square feet are in 2 square meters?

3) The smallest "living" thing is probably a type of infectious agent know as a viroid. Viroids are plant pathogens that consist of a circular loop of single-stranded RNA, containing about 300 bases. (Think of the bases as beads strung on a circular RNA string.) The distance from one base to the next (measured along the circumference of the circular loop) is about 0.40 nm.

(a) What is the diameter of a viroid in m?

(b) What is the diameter of a viroid in µm?

(c) What is the diameter of a viroid in in.?

Your teachings are greately appreciated:)

Answer 1

Conversion bridges.

Find a known conversion ratio and use that for
finding the proportion for the unknown quantity.

1.90 kilometer / hour

kilometer to meter and hour to minute to second
1 to 1000 and 1 to 60 then 1 to 60

1/1000=1.9/x
x=1000*1.9
=1,900

1/60 is like * 60 -> 1,900*60=1.14 * 10^5
again, 1/60 is like *60 -> 1.14*10^5 * 60=6.84*10^6

The final unit is
6.84 * 10^6 m/s

General rules:
1. Use cross multiplication proportions for numerator
2. Multiply by the "per" unit(per hour, per minute, etc)
if the unit being converted to is a lesser quantity of time.
Otherwise divide insteand of multiply.



Convert from 2 ft^2 to x cm^2
2 ft^2=(2^(1/2) * ft)^2

12 inches to 1 foot

12/1 = x/( 2^(1/2) )
x=12*2^(1/2) inches
=12*sqrt(2) inches

2.54 cm to 1 inch

2.54/1 = x/( 12*sqrt(2) )
x=2.54*12*sqrt(2)
=30.48*sqrt(2) cm

Back to original:
(2^(1/2) * ft)^2
(30.48*sqrt(2) * cm )^2
30.48^2 * 2 cm^2
1,858 cm^2


Same process for (b). Factor out the exponent and
convert the inner units then when finished with conversions
distribute the exponent to each of the factors.



Circle with circumference of 0.4 nm or 0.4 * 10^(-9) m
circumference=2(pi)r
0.4*10^(-9)=2(pi)r
r=0.4*10^(-9)/[ 2(pi) ]
=0.2*10^(-9)/ (pi) m

d=2r
d=0.4*10^(-9)/ (pi) m

um= micrometers = 10^(-6)

d=0.4*10^(-3)/ (pi) um

d=0.4*10^(-7)/ (pi) cm

2.54 cm to 1 inch

2.54/1= [0.4*10^(-7) / (pi)]/x
2.54x=0.4*10^(-7) / (pi)
x=0.4*10^(-7) / [ 2.54* (pi) ]

d=1.575*10^(-8) / (pi) inches

Answer 2

4.64 x 10^14 1.5x 10^8 If I remember right. The gentleman above is correct about the number of digits. I thought I had remembered that multiplication of exponents is simply adding the exponent componenet after multiplying the numeral. And division was subtracting. Good luck though. Good luck!

Answer 3

None of these are actually physics questions. They are just about the conversion of units and simple math.

They might be contained in the first chapter of a physics textbook, but no. If you can't already figure out how to convert them based on the info in your book, you'll never learn anything here - no matter who shows you their work.