a problem while SOLVING "average speed" .. HEEEEELLLPPP?

Question

IVE JUST BOUGHT a book called " new higher physics .. 2ed"

the train travels the 75km between edinburgh and glasgow... in 50 min (0.83 hours) its average speed is

average speed = 75km
------
0.83 h
average speed = 90km h(-1)

WHAT THE HELL IS (-1) how can we calculate this (-1) .. and what does it mean?!

Answer 1

I am not sure what your book is referring to, but here
is some information.

Velocity:
velocity=distance/time

velocity=75km/0.83h
=90 km/h


For some reason your author chose to write the exponent
of the unit as a negative number. When encountering
a negative exponent transfer the base and exponent
to the other side of the fraction and change the sign
of the exponent(positive now).

x^(-3)*y^(2)*z^(4)*m^(-5)
= y^(2)*z^(4) / ( x^3*m^5 )

Answer 2

Yup, as said above is true. the number in parantheses is just an exponent. Negative exponents (like -1 ) in a product (something times something) mean they could be re-written as the denominator of a fraction instead.

When you see a "unit(-1)" it just means "per unit". Literally it is saying "times the unit to the negative 1st power"

Likewise, when you run across "unit (-2)" that will mean "per unit squared". It sounds like the acceleration of gravity will be written as "9.8 m sec (-2)" in this book. 9.8 meters per second squared being the same as 9.8 meters times seconds to the negative 2nd power". Using just simple ASCII, this value might be written as "9.8 m/s^2" or "9.8 m*s-2" or some such.

The notation you have is kind of wierd, using parantheses like they didn't have superscript fonts, but you should be able to take these answers and run with it.

Hope that gives a little more clarity!

Answer 3

Likely the (-1) is an exponent to Hr and means the inversion of Hr or 1/Hr. In your example it would mean per hour.

Answer 4

"h(-1)" = per hour so km h(-1) means km/hr