1) A basic Impulse momentum problem - Two men pushing a stalled car generate a net force of +680N for 7.2s. What is the final momentum of the car ?

2)Two friends Al and Jo, have combined mass of 168kg. At an ice skating rink they stand close together on skates, at rest and facing each other, with a compressed spring between them. The spring is kept from pushing them apart because they are holding each other. When they release their arms, Al moves off in one direction at a speed of 0.90m/s, while Jo moves off in the opposite direction at a speed of 1.2m/s. Assuming that friction is negligible, find Al's mass ?

3)An automatic dryer spins wet closthes at an angular speed of 5.2rad/s. starting from rest the dryer reaches its operating speed with an average acceleration of 4.0 ras/sec^2. How long does it take the dryer to come up to speed ? I came up with 0.325 sec but is that right ?

4)Tangential Speed - A string trimmer is a tool for cutting grass and weeds; it utilizes a lenth of nylon "string" that rotates about an axis perpendicular to one end of the string. the string rotates at an angular speed of 47 rev/s, and its tip has a tangential speed of 54 m/s. What is the lenght of the rotating string ?

Any assistance, clarification you could provide would be most helpful.