Physics 113 –Morning Session, Summer 2007
To be turned in at the end
each discussion session, stapled on top of Participation Points #3, #2, and
#1
Student’s name _____________________ Total previous points
accumulated:
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9.1- 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?
9.2- 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.
9.3- 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?
10.1- 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?
10.2- Analog
of
10.3- 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.
11.1- 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.
11.2- 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?
11.3- 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.