Measuring Mass of a Hanging Weight: Stephen's Question

[StephenDoty]

We did a lab where we had to measure the mass of a weight that was hanging from an air track which pulled the glider through two timegates positioned above the air track.

I have to find the force of the hanging weight. F=mg my first mass was .27004kg and the gravity is obviouly 9.8m/s/s.

So do I use F=.27004kg * (9.8m/s/s)
or
F= .27004kg * (-9.8m/s/s)

Do I put the negative sign with the gravity as the force is downward with the hanging weight?

Thank you
Stephen

 

[rock.freak667]

The - sign only indicates a direction. So you can leave it as +ve once you remember that putting g as +ve says that the downward direction is taken as +ve.

 

[Moetasim]

,

Great question, Stephen! In this case, you would use the first equation, F=0.27004kg * (9.8m/s/s). The negative sign is not necessary because the force of gravity is always directed downwards, regardless of the direction of the glider's movement. However, it is important to keep in mind that the force of gravity is a vector quantity, meaning it has both magnitude and direction. So, for example, if the glider was moving in the opposite direction (upwards), you would need to use the negative sign to indicate that the force of gravity is acting in the opposite direction. Keep up the good work in your experiments!