Astronomy question,
what keeps supernova explosions from being seen?

You hang a book bag on a spring scale and place the bag on a platform scale so that the platform scale reads 23.7n and the spring scale reads 13.8n. what is the magnitude of the force that earth exerts on the bag?

What happens when the vapor pressure of a liquid is equal to the external pressure?

How to know which equation of motion to use where?explain