# Math Help - help with units maths

1. ## help with units maths

hi

im doing a course in complex maths for the building industry and have to pass this maths section before i go on. maths was a bad subject for me so now i need to learn. my biggest problem is notation such as one question is

convert 39cm to km and answer in scientific notation

would that be 100000cm = 1km therefore 39/100000=0.00039

is that right

and the one thats got me is

a mass rests on an area of 80mm2 and exerts a force of 320 kg m/s2. express the pressure exerted on this area in kN/cm2

i worked it out but not sure if im right

so can you all help me out i will post more soon

cheers dan

2. Originally Posted by aadkeski
hi

im doing a course in complex maths for the building industry and have to pass this maths section before i go on. maths was a bad subject for me so now i need to learn. my biggest problem is notation such as one question is

convert 39cm to km and answer in scientific notation

would that be 100000cm = 1km therefore 39/100000=0.00039

is that right
Yes, but it wants the answer in scientific notation, so in this case it would be

$3.9 ~10^{-4}$

RonL

3. Originally Posted by aadkeski
and the one thats got me is

a mass rests on an area of 80mm2 and exerts a force of 320 kg m/s2. express the pressure exerted on this area in kN/cm2

i worked it out but not sure if im right

so can you all help me out i will post more soon

cheers dan
What does 320 kg m/s^2 mean. The force that will accelerate 1 kg
at 1 m/s^2 is 1 N, so on the face of it this is a force of 320 N.

80 square mm = 80/10000 = 8/1000 = 0.008 cm^2

Therefor the pressure is 320/0.008=40000 N/cm^2, or
40 kN/cm^2.

RonL

4. THANKS

when i see it all worked out its easier to understand. i have a heap more questions so should i post here.

thanks again

5. Originally Posted by aadkeski
THANKS

when i see it all worked out its easier to understand. i have a heap more questions so should i post here.

thanks again
Yes, go ahead.

RonL