Note this has a piece on relative velocities, too, part of Lecture 5 but not assigned until Homework 1B.

6. one point, from Lectures 5, 6, involves calculation, sketches

(a) .4 from Lecture 5, Translation Rules for Relative Motion. If a ball is thrown with speed 14m/s relative to the passer, and the receiver is running away from the passer with speed 8m/s, how fast will the ball hit the receiver's hands? (.1)
If the receiver is running toward the passer with speed 6m/s, how fast will the ball thrown with speed 14m/s hit the receiver's hands? (.1)
Which of these is a hard and which a soft catch? (.1)
Sketches help here, so do a simple one for each case, and on your sketches label the various speeds clearly with subscripts. Then be sure you also write the relevant equations and label the various speeds clearly as you show your work. (.1) Box your answers.

(b) .6 from Lecture 6, Analysing a Collision. Use Conservation of Momentum to solve this problem: A bike plus rider of mass 75 kg with speed 20 m/s runs headon into a small car plus driver of mass 600 kg with speed 16 m/s. The bike sticks to the car and the whole system proceeds in the direction the car was going. How fast is the accident traveling? (.1)
Sketch this one, too, before and after, with all the quantities and directions labeled (.1). Write the general conservation equation (.1), then the specific equation for this case (.1), and show your work (.2). Box your answer.

Revised September 22, 1997.