- #1
Remle
- 12
- 8
- Homework Statement
- You start walking home from school. After walking 1.3 km North, you get a phone call on your cell from your mom asking if you can meet her at the mall. You will have to turn around and walk 2.5 km South. Determine your distance and displacement to get to the mall.
- Relevant Equations
- d=df-di
I having a little bit of problem with ##\Delta d = d_f - d_i##. When substituting fo ##d_f## and ##d_i##, should I follow the signs rule (positive or negative)?
For example,
The problem shows that the displacement is ##1.2~\rm{km}, south## by solving ##\Delta d = -2.5 + 1.3## and I get that, but if I use the formula above the equation would appear like this ##\Delta d = -2.5 - 1.3## which gives me ##-3.8~\rm{km}## or ##3.8~\rm{km}, south##.
What am I missing?
source: http://www.studyphysics.ca/2007/20/01_kinematics/08_velocity.pdf
For example,
The problem shows that the displacement is ##1.2~\rm{km}, south## by solving ##\Delta d = -2.5 + 1.3## and I get that, but if I use the formula above the equation would appear like this ##\Delta d = -2.5 - 1.3## which gives me ##-3.8~\rm{km}## or ##3.8~\rm{km}, south##.
What am I missing?
source: http://www.studyphysics.ca/2007/20/01_kinematics/08_velocity.pdf