Twenty is the of potassium.
a) charge
b) atomic mass
c) atomic number
d) number of neutrons

An observer that stands still as the electron moves by him, will observe

Because light travels in a straight line and casts a shadow, isaac newton hypothesized that light is

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. but she does have devices to measure distance and time accurately. she knows her own mass is 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?