What is the speed of a wave that has a wavelength of 20 cm and a period of 0.5 s? 4 cm/s 40 cm/s 0.025 cm/s 10 cm/s

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

Henry, whose mass is 95 kg, stands on a bathroom scale in an elevator. the scale reads 830 n for the first 2.4 s after the elevator starts moving, then 930 n for the next 2.4 s. part a what is the elevator's speed 4.8 s after starting? express your answer with the appropriate units.

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?