# Homework Help: Post Lab Question

1. Feb 3, 2013

### Habibrobert

Hello everyone, I'm working on a physics postlab due tomorrow, and I'm just really skeptical that the answers I am getting so far are correct, I just feel like the problems are designed to "trick you" because of the values you are looking for are on the graph. could you guys please take a look at it and tell me how to do this particular page of the prelab correctly? The set up is a cart on a frictionless track that has a string tied to it which is also tied to some weight (the prelab calls it a hanger) that is hanging down and pulling on the cart. Attached a screen shot of the prelab

Thanks very much!

File size:
70.3 KB
Views:
116
2. Feb 3, 2013

### Staff: Mentor

Check the decimal point for the force.
Where is that force measured?
How did you get the mass of the hanger?

3. Feb 3, 2013

### Habibrobert

The force is measured from the car, before and after it was released. I used F=m*a to find the mass of the hanger, but I feel like that is wrong.

4. Feb 3, 2013

### Staff: Mentor

In other words, it is the tension of the string connecting both?

It is hard to tell if you don't add which a and F you used. The mass looks wrong.

5. Feb 4, 2013

### Basic_Physics

Is the force sensor mounted on the cart and the string tied to the force sensor?
• Accleration ok.
• Decimal point in force on force sensor while accelrating wrong. I am not sure if they want the negative though. All it means is that the force sensor is registering a pull , which is displayed as a negative value. A push on the sensor will be displayed as a positive value.
• Mass of the hanger wrong. The force sensor reads the (full) tension in the string when the cart is stationary.