Using Newton’s first law of physics, which explains why it is harder to swim in water with a current (like the ocean) than in contained water (like a pool)? A.
Perpetual motion can only be interrupted by an unbalanced force.
B.
The current will interfere with perpetual motion more than still water.
C.
It takes much more strength to swim if there is a current than in a pool.
D.
Still water is an immovable object, but currents have their own momentum.

Aparticle of mass m is placed in a one-dimensional box of length l. the box is so small that the particle’s motion is relativistic, so that e p2/2m is not valid. (a) derive an expression for the energy levels of the particle using the relativistic energy–momentum relation and the quantization of momentum that derives from connement. (b) if the particle is an electron in a box of length l 1.00 1012 m, nd its lowest possible kinetic energy. by what percent is the nonrelativistic formula for the energy in error?