# Terminal Speed

1. May 30, 2014

### cuongbui1702

1. The problem statement, all variables and given/known data

2. Relevant equations
That is the solution:

3. The attempt at a solution
I think ε≠Bvl because ε = - dø/dt=- Bd(v.t)/dt, v is not constant.
Why ε=Bvl???

2. May 30, 2014

### CAF123

The induced emf in the loop is related to the change in flux through a surface whose boundary is the loop: $$\epsilon = -\frac{\text{d} \phi}{\text{d}t} = -\frac{\text{d}}{\text{d}t} \int_S \mathbf{B} \cdot \mathbf{dS}$$
In your case, the B field is of constant magnitude and direction and dS instantaneously is Ldx.

3. May 30, 2014

### dauto

dø/dt = d(B. Area)/dt = d(BLx)/dt = BL dx/dt = BLv.