# Find Ratio of vb/vc for Person Homework Statement

• lpcampbe
In summary, a person standing on a sheet of ice fires a gun parallel to the ground, with a standard cartridge resulting in a 17-g bullet shot forward at 280 m/s and a recoil speed for the person of vc. When a blank cartridge is used, a mass of 0.13g is shot forward at 53 m/s and the recoil speed is vb. The ratio vb/vc can be found by considering conservation of momentum and the inverse ratio of their masses. The mass of the person is not given and should not be assumed.
lpcampbe

## Homework Statement

A person is standing on a sheet of ice so slippery that friction may be ignored. This individual fires a gun parallel to the ground. When a standard cartridge is used , a 17-g bullet is shot forward with a speed of 280 m/s, and the person recoils with a speed of vc. When a blank cartridge is used , a mass of 0.13g is shot forward with a speed of 53 m/s , and the recoil speed is vb. Find the ratio vb/vc.

mass of bullet = 0.017 kg
mass of blank = 1.3e-4 kg

KE = 1/2mv^2 ?

## The Attempt at a Solution

I tried using that equation and solved for KE of the bullet (666.4 J) and the KE of the blank (0.1825 J) but I don't know if that's useful or not. I'm not given the mass of the person, and I don't just want to assume 60 kg. I know I'm supposed to attempt to do the problem before asking for help, but I don't even know where to start.

Here, remember that momentum is always conserved. Because of this, you can say that the total momentum change is 0.

Also keep in mind that the mass of the man never changes in either situation. Think about this.

The kinetic energy (KE) would not be helpful here, becase chemical energy is being converted into kinetic energy when the gun is fired. Momentum, however, is helpful.

Think of the system (man plus pistol plus bullet) splitting in two. The two parts (man plus pistol) and (bullet) will have equal but opposite momenta. Their speeds will therefore be in the inverse ratio of their masses. In practice, the bullet would be so small, that the man and his paraphernalia may be assumed to have the same mass throughout the experiment.

## 1. What does "Find Ratio of vb/vc for Person Homework Statement" mean?

The statement is asking for the ratio between two variables, vb and vc, for a specific person. This ratio is likely related to a homework assignment or problem in a scientific or mathematical field.

## 2. How do I find the ratio of vb/vc for a person?

To find the ratio, you will need to know the values of both vb and vc for the specific person. Then, divide the value of vb by the value of vc. This will give you the ratio of vb/vc for that person.

## 3. Why is it important to find the ratio of vb/vc for a person?

The ratio of vb/vc can provide valuable information about the relationship between these two variables for a person. It can also help in solving equations or problems related to these variables.

## 4. Can the ratio of vb/vc be greater than 1?

Yes, the ratio of vb/vc can be greater than 1. This means that vb is greater than vc for the specific person.

## 5. Are there any specific units for the ratio of vb/vc?

The units for the ratio of vb/vc will depend on the units of the variables vb and vc. If both variables have the same units, then the ratio will be unitless. If the units are different, the ratio will have the units of vb/vc.

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