# Significant digits including only one zero

1. Mar 9, 2013

### alingy1

1. The problem statement, all variables and given/known data
The problem asks us to find deceleration from 60km/h to 0km/h in 1,2 seconds.

2. Relevant equations
The speed formulas

3. The attempt at a solution
I know how to apply the formula. However, in the problem, it is written 0km/h. How many significant digits is that? How many significant digits should i have in this problem for the final result?

2. Mar 9, 2013

### mell0r

You should have 2 in your answer as acceleration is the change in velocity (i.e. 60km/h in this case). The 0km/h can be ignored in the case of significant digits

3. Mar 9, 2013

### alingy1

Thank you

Thanks that's what I wanted to know. The zero is confusing. Also, for my lab report, I have to jot down the speed of a small toy according to the time passed. At the beginning, the toy is not moving. Should I put 0m/s or the number of significant digits put for the other data, since we can't really be sure the toy is not moving very very slightly?
Thanks again.

4. Mar 9, 2013

### mell0r

If it's not moving initially, 0 m/s will be fine.

5. Mar 9, 2013

### lewando

"Not moving" implies zero km/h with extreme precision. That is different from 0km/h. What would your answer be if the original question was looking for 60km/h to 1km/h?