Practice problems

Relative velocity

A) A student is sitting in the back of a pick up truck traveling down Chestnut street at 15 m/s. He is using a sling shot to launch water balloons at 20 m/s, with the launcher pointed back at a 45 degree angle with the side. What is the speed and direction that the balloon flies into the crowd of students on the sidewalk?

B) A small plane is flying due north (relative to the air) at a speed of 160 mph. However, there is a wind out of the west at 60 mph at this elevation. Where will the plane be relative to its starting position after 1.5 hours?

C) A boat capable of traveling at 10 m/s in water is set to cross a river flowing at 6 m/s. In what direction should the pilot point the boat so the resulting motion is directly across the river? How long will it take to cross the 40 m wide river?

Projectile motion

A punter kicks a ball down field. It leaves his foot, 1.5 m above the ground, at a speed of 15 m/s and at an angle of 50 degrees from the horizontal. What is the hang time, and how far does it go?