An automobile travels on a straight road 35 km at 30 km/h. It then continues in the same direction for another 35 km at 60 km/hr. What is the average velocity of the car during the full 70 km trip? PLZ SHOW WORK.

Can someone explain to me how to do this problem ?

•• al and bert are jogging side-by-side on a trail in the woods at a speed of 0.75 m/s. suddenly al sees the end of the trail 35 m ahead and decides to speed up to reach it. he accelerates at a constant rate of 0.50 m/s2, while bert continues on at a constant speed. (a) how long does it take al to reach the end of the trail? (b) once he reaches the end of the trail, he immediately turns around and heads back along the trail with a constant speed of 0.85 m/s. how long does it take him to meet up with bert? (c) how far are they from the end of the trail when they meet?

What is friction? how does it affect the motion of an object?