Speeding truck slams on the brakes and accelerates at -7.40m/s^2 Before coming to a stop. It leaves skid marks on the pavement that are 43.1m long. How fast was the truck going before it slammed on the breaks?

Two identical small charged spheres are a certain distance apart, and each one initially experiences an electrostatic force of magnitude f due to the other. with time, charge gradually leaks off of both spheres. when each of the spheres has lost half its initial charge, the magnitude of the electrostatic force will be

What happens to the light rays when they hit the specimen?

Who was the first scientist to measure speed as distance over time?