What is the difference between historical time and a quantity of time

How many times did thomas edison mess up the light bulb

Using the free-body diagram, calculate the net force acting on the sled. is the sled in a state of dynamic equilibrium?

Abeam of electrons moves at right angles to a magnetic field of 4.5 × 10-2 tesla. if the electrons have a velocity of 6.5 × 106 meters/second, what is the force acting on the electrons? the value of q = -1.6 × 10-19 coulombs.