# 9yr old 7th grader needs help!

1. Sep 18, 2008

### LisaandCaiti

I have a problem in my science book,we think the teachers edition may have a mistake? Can someone look at my problem and explain how to find the answer? I am home schooled, and like mom said, 7th grade was too many years ago!

Calculate mass: You push yourself on a skateboard with a force of 30N and accelerate at 0.5 m/s squared. Find the mass of the skateboard if your mass is 58kg.

We keep coming up with a different answer than the book. Can someone explain this so we can make sure we are doing it correctly?

Thank You!

<< personal e-mail address edited out by berkeman >>

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

Last edited by a moderator: Sep 18, 2008
2. Sep 18, 2008

### mgb_phys

The equation is force = mass * acclearation or F=ma
Since we know f and a and want m we have to re-arrange the formula this gives m=f/a
If you plug in the numbers you get m = 30N/0.5ms-2 = 60kg
Since you have a mass of 58.5kg the mass of the skateboard is the difference.

3. Sep 25, 2008

### cancer501

you divide 30n by 0.5 m/s and you will get ur anwser which you then subtaract 58 from and you will get ur anwser it will have this unit of measure kg*m/s N