Why do my hair change colors?

Aperson walks first at a constant speed of 4.89 m/s along a straight line from point a to point b and then back along the line from b to a at a constant speed of 2.95 m/s. what is the average speed over the entire trip?

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

Atruck travels at an average speed of 70 km/hr. if it travels 100 km in the first hour, how far will it go the second hour of a 2 hour trip? if you could also give me the steps that would great.