A passenger railroad car has a total of 8 wheels. Springs on each wheel compress--slightly--when the car is loaded. Ratings for the car give stiffness per wheel (the spring constant, treating the entire spring assembly as a single spring) as 2.8×10^7N/m. When 30 passengers, each with average mass of 80 kg, board the car, how much does the car move down on its spring suspension?

Explanation:

mg = kx

x = mg/k

x = 30(80)(9.8)/2.8e7 = 0.00084 m  ≈ 1 mm

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.