4. A 100 kg crate sits on the concrete floor of a warehouse. The static coefficient of friction of wood on concrete is .62. Kinetic is 55.

a Calculate the force needed to get the crate moving from rest.

b. Calculate the force needed to keep the crate sliding at a constant velocity

Calculate the force needed to accelerate at 3.2 m/s.

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?