HW4 5A F21.pdf - Homework 4 Physics 5A Due Wednesday...

Homework 4
Physics 5A
Due Wednesday 9/22/21
(1) (10 pts) Matt is trying to move a crate of all of his physics books into his new house.
The crate is heavier than Matt himself and rests on a rough floor. The coefficient
of static friction between the crate and the floor is the same as that between Matt’s
shoes and the floor. Can Matt push the crate? (Fig. 1 right)
Figure 1.
left: An approximation of the force between 2 atoms in a diatomic
molecule right: Matt pushing a crate
(2) KK 3.2 (10 pts)
(3) KK 3-5 (10 pts)
(4) KK 3.22 (10 pts)
(5) KK 3.10 (10 pts)
(6) KK 3.12 (10 pts)
(7) KK 3.17 (10 pts)
(8) A uniform circular plate of radius 2R has a circular hole of radius R cut out of it
as shown in Fig. 2. The center C’ of the smaller circle is a distance 0.8R from the
center C of the larger circle. Where is the center of mass of the plate? hint: try
subtraction.
(9) KK 4.1 (10 pts)
(10) An artillery shell accidentally exploded at the top of its parabolic trajectory. The
horizontal distance between the launch point and the point of the explosion is L.
The shell breaks into 2 pieces that fly apart horizontally. The larger piece has 3
times the mass of the smaller piece. To the surprise of the scientist in charge, the
smaller piece returns to Earth at the launch point. How far away does the larger
piece land? Neglect air resistance and earth’s curvature . (10 pts)
(11) Challenge Problem: Math tricks to solve non-linear friction problems (20 pts ...
remember you can get a 100 without attempting this)
If you have ever stuck your hand out the window of a moving car, you may have
noticed the wind pushing back on your hand. This air resistance is a force directed
in the opposite direction of motion and increases with the velocity of the object
(in essence, air molecules collide with your hand at increasing speeds, resulting in
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