# How fast is the rod moving after it has traveled 8.00 m down the rails?

• sweetipie2216
In summary: ILB/mIn summary, the conversation discusses the use of an electromagnetic rail gun to fire a projectile using a magnetic field and an electric current. The problem involves a conducting rod placed across two parallel conducting rails with a battery connected between them. A magnetic field and current are also present. The formula for calculating the speed of the rod is discussed, but there is confusion about the use of the formula. The correct formula is determined to be F = ILB, leading to the final answer for the rod's speed.
sweetipie2216

## Homework Statement

An electromagnetic rail gun can fire a projectile using a magnetic field and an electric current. Consider two parallel conducting rails, separated by 0.530 m, which run north and south. A 49.0 g conducting rod is placed across the tracks and a battery is connected between the tracks, with its positive terminal connected to the east track. A magnetic field of magnitude 0.750 T is directed perpendicular to the plane of the rails and rod. A current of 2.00 A passes through the rod.
If there is no friction between the rails and the rod, how fast is the rod moving after it has traveled 8.00 m down the rails?

## Homework Equations

a=(IL(([mu0(I))/(2\pi*r)))/m

## The Attempt at a Solution

(2(.530)(4pi-7(2))/(2pi(.53))/.049 = 1.63e-5
sqrt{2*1.63e-5*8}=.016

this answer is wrong. can you please tell me what i am doing wrong and help me out?Thanks.

Sweet, I don't recognize that formula! Can you derive it from basic formulas for us? I would expect you to use Fm = I*L*B in this problem - the formula for the magnetic field causing a force on a current.

i got the answer, thanks for trying to help

Sorry, I'm still not with you. I see you are using F = ma but why not
F =ILB? Where does the mu and pi come from? I would begin with
F = ma
ILB = ma

## 1. How is the speed of the rod calculated?

The speed of an object is calculated by dividing the distance traveled by the time it took to travel that distance. In this case, the distance traveled is 8.00 m, so the speed of the rod would be calculated by dividing 8.00 m by the time it took to travel that distance.

## 2. What is the unit of measurement for the speed of the rod?

The unit of measurement for speed is meters per second (m/s). This unit indicates the distance traveled in meters divided by the time taken to travel that distance in seconds.

## 3. Is the speed of the rod constant while traveling down the rails?

Assuming there are no external forces acting on the rod, the speed of the rod will remain constant while traveling down the rails. This is because the rod will continue to move at the same speed unless a force is applied to change its speed or direction.

## 4. Does the length of the rails affect the speed of the rod?

No, the length of the rails does not affect the speed of the rod. The speed of the rod is determined by the distance it travels and the time it takes to travel that distance, not the length of the rails it travels on.

## 5. Can the speed of the rod be greater than the speed of light?

No, according to Einstein's theory of relativity, the speed of light is the maximum speed at which all matter and information in the universe can travel. Therefore, the speed of the rod cannot exceed the speed of light.