Do you see a problem do you see with $\mathbf{F} = \dfrac{d\mathbf{p}}{dt}$ with regard to relativity? We still define $\mathbf{p} \equiv \gamma m\mathbf{v}$.
1. There's no problem at all
2. Yup there's a problem, and I know what it is.
3. There's probably a problem, but I don't know what it is.
Can we define a 4-force via the 4-momentum?
$$\dfrac{dp^{\mu}}{d\tau} = K^{\mu}$$
Is $K^{\mu}$, so defined, a 4-vector?
1. Yes, and I can say why.
2. No, and I can say why.
3. None of the above.
Note:
* Correct Answer: A
To match the behavior of non-relativistic classical mechanics, we might tentatively assign which of the following values to $\mathbf{K} = K^{1,2,3}$:
1. $\mathbf{K} = \mathbf{F}$
2. $\mathbf{K} = \mathbf{F}/\gamma$
3. $\mathbf{K} = \gamma\mathbf{F}$
4. Something else
Note:
* Correct Answer: C
A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
If we switch to a different Galilean frame (a low speed Lorentz transform), is the acceleration $\mathbf{a}$ different?
1. Yes
2. No
Note:
* Correct answer: B
A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
If we switch to a different Galilean frame (a low speed Lorentz transform), is the particle velocity $\mathbf{u}$ different?
1. Yes
2. No
Note:
* Correct answer: A
A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
If we switch to a different Galilean frame (a low speed Lorentz transform), is the magnetic field $\mathbf{B}$ different?
1. Yes
2. No
Note:
* Correct answer: A
A charge $q$ is moving with velocity $\mathbf{u}$ in a uniform magnetic field $\mathbf{B}$.
$$\mathbf{F} = q\mathbf{u}\times\mathbf{B} = m\mathbf{a}$$
Suppose we switch to frame with $\mathbf{v} = \mathbf{u}$, so that in the primed frame, $\mathbf{u}’ = 0$ (the particle is instantaneously at rest). Does the particle feel a force from an E-field in this frame?
1. Yes
2. No
3. depends on details
Note:
* Correct answer: A