What is the difference between velocity and speed? ?

What occurs during a combustion reaction

When you hold a rectangular object, how does the area of the side that is resting on your hand affect the pressure and the force that the object exerts?

The theory that light exists in quantized "chunks" was proposed in response to which of the following? a. electron interference patterns o b. discovery of planck's constant o c. the ultraviolet catastrophe o d. emission spectra