Physics 113 –Morning Session, Summer 2006

Participation Points #4

To be stapled on top of Participation Points #1, 2, 3

 


Student’s name _____________________           Total previous points accumulated:

 

 

 

 

 

 

 

 

 

 

 

10.1            Momentum of the center of mass. A 1000 kg car at velocity v1=2.5 i + 10 j m/s skids on a frictionless icy road, it hits a 500 kg wagon moving at v2=  4 i + j m/s. If they stay together, what is their velocity?

 

 

 

 

 

 

 

 

11.1            Inelastic collision. A 1000 kg car moving at 10 km/h collides with a 1500 kg car moving in the same direction at 5 km/h. The slower car is equipped with spring bumpers with spring constant 20kN/m. Find the maximum compression of the spring.

 

 

 

 

 

 

 

 

11.2              Elastic collision. While playing a ball in the street, a child accidentally tosses a ball at 20m/s toward the front of a car moving toward him at 15 m/s. What is the speed of the ball after it rebounds elastically from the car?

 

 

 

 

 

 

 

 

 

 

12.1            Torque. A torque of 100Nm is required to start a revolving door. If a child can push 50N North while the door is aligned in the SW direction, how far from the axis of rotation must he apply this force?

 

 

 

 

 

 

 

12.2              Analog of Newton’s Law. A 2.5kg block rests on a 300 slope and attached by a negligible mass string to a solid drum of mass 1kg and radius 5cm. When released, the block accelerates down the slope at 2m/s2. What is the coefficient between block and slope?

 

 

 

 

 

 

 

 

 

12.3      Rolling motion. A round object like a sphere or wheel may be characterized by a rotational inertia of the form I=αMR2, with  α a constant. Derive an expression for the final speed of such an object if it starts from rest and rolls without slipping down an incline of vertical height h.

 

 

 

 

 

 

 

 

13.1          Vector cross product. Find a force vector that when applied at the point x=2m, y=1m, will produce a torque τ=5 k Nm about the origin.

 

 

 

 

 

 

 

13.2              Angular momentum. A 5cm diameter baseball has a mass of 100g and is spinning at 200 rad/s. What is the magnitude of its angular momentum?

 

 

 

 

 

 

 

13.3     Conservation of angular momentum. A turntable of radius 20cm and rotational inertia 0.01kg.m2 is spinning freely at 20rpm about its central axis, with a 20g mouse on its outer edge. The mouse walks from the edge to the center, find the new rotation speed.