Calculating Inertia Ratios of Carts on a Low-Friction Track

[emily081715]

Homework Statement

The vx(t) curves for two carts, A and B, that collide on a low-friction track are shown below:

What is the ratio of their inertias?

Homework Equations

the ratio i am looking for is mB/mA

The Attempt at a Solution

I believed that the ration was 1/2 however that is not correct and i do not see how there can be another ratio

 

[mfb]

How did you get the value 1/2?
Which mass is larger?

 

[emily081715]

How did you get the value 1/2?
Which mass is larger?

is the cart of mass B not larger because it had a smaller change is speed, meaning it has a larger inertia and greater mass. i got the 1/2 ratio because the mass of cart A is double the mass of cart B

 

[mfb]

is the cart of mass B not larger because it had a smaller change is speed, meaning it has a larger inertia and greater mass.

Correct, cart B has a larger mass.

because the mass of cart A is double the mass of cart B

This is in contradiction to what you said immediately before that.

 

[emily081715]

I meant cart B is double the mass of cart A. But the ratio isn't 2/1

 

[mfb]

But the ratio isn't 2/1

Why not?
You can try to estimate the changes a bit better from the diagram, that will give a value very close to 2/1, but usually you are not supposed to measure individual pixels on problems like this.

 

[emily081715]

Why not?
You can try to estimate the changes a bit better from the diagram, that will give a value very close to 2/1, but usually you are not supposed to measure individual pixels on problems like this.

i already tried the ratio and it was wrong which is why I'm confused for the question

 

[emily081715]

i already tried the ratio and it was wrong which is why I'm confused for the question

turns out the answer was 2.1

 

[mfb]

Okay, bad problem statement. Giving something that is so close to 2 and then expecting students to count pixels is a very bad style.