How is everyone doing? What have you been up to?

A10.0 kg cart and a 15kg cart are locked together with a compressed spring between them. they are then released so that the spring pushes the two carts apart. the 10.0 kg cart is moving at 4.5 m/s afterward. how fast is the 15kg cart moving? 3.0 m/s 2.0 m/s 4.5 m/s 5.0 m/s

Which type of wave can travel without a medium

The speed of light in a material is 0.50 c. what is the critical angle of a light ray at the interface between the material and a vacuum?