If r and s are vectors that depend on time, prove that the product rule for differentiating products applies to r. s, that is, that d/dt (r. s) = r· ds/dt + dr/dt ·s.

Can someone explain to me how to do this problem ?

Calculate the mass of an object that has a momentum of 100kg x m/sec and velocity of 4 m/sec

Choose the most likely outcome of this scenario: jen decided to go bike riding without a helmet. while no one is around during her ride, she is thrown from her bike when her wheel goes into a pothole. she is not injured, but she is terrified to get back on her bike. what happens next? a. her physical health is affected even though she wasn't hurt. b. her mental and emotional health are affected because she is afraid to get back on her bike. c. her social health is affected because she is worried her friends saw the fall. d. her overall health is not affected at all by her fall.