TEACHER'S TEACHERS'S TEACHER'S TEACHER'S
Ken Cheney
10/28/2005
4:59/C0
Physics 31A Test Four
1. JUMP START
You plan to start your motorcycle by running up to it, jumping on,
and using your combined speed to start the engine. How many f/s must
you be going when you run up if the final velocity to start is 12 f/s,
you weigh 110 lb and it weighs 250 lb?
12*(110+250)/110
a. 14.5, b. 24, *c. 39.3, d. 43.4, e. 118
2. MERRY GO ROUND
How many revolutions will a merry-go-round make while stopping if
the initial velocity is 17 revolutions per minute, and the acceleration
is 18 revolutions per minute per minute?
17**2/(2*18)
a. 2.55, *b. 8.03, c. 12.3, d. 21.6, e. 29.2
3. OMEGA SQUARED
Durive the equation "omega squared = omega zero squared + 2 alpha
theta" . Start from the linear equilvent.
4. YOUR ACCELERATION
What acceleration (ft/ss) can your car produce at a velocity of
110 ft/s if it weighs 2,200 lb and has 200 HP? 1HP=550 ft lb/s
200*550*32/2,200/110
a. .0264, b. 4.44, c. 5.58, d. 18.9, *e. 14.5
5. RESCUE
A uniform 220 lb telephone pole is 110 feet long. 38 feet of the
telephone pole are sticking out over the Grand Canyon, while the rest
of the pole lies on the ground. If you weigh 180 lb, how many feet can
you walk out on the pole to rescue a massless cat trapped at the end of
the pole?
220*(110/2-38)/180
*a. 20.8, b. 24, c. 43.2, d. 69.3, e. 83.1
6. AUTO BRAKE
You are designing a brake to stop a saw blade within .76
revolutions after the motor is turned off. The initial speed is 1,200
revolutions per minute. The blade has a radius of .052m and a mass of
.34 kg. Find the torque required in nt m. I=m R R/2 for a uniform
disk.
Physics 31A Test Four - Ken Cheney - V. 4:59/C COPY 0 PAGE 2
.34*.052*.052*1,200*1,200*PIX(1)/(7200*.76)
a. .332, *b. .76, c. .863, d. 2.38, e. 2.68
7. GUNSMANSHIP
You forget to hold your gun against your shoulder and it recoils
into you. How many Joules of kinetic energy end up in your sholder?
Assume you and the gun move together in the end.
Masses: YOU=90 KG, GUN=10 KG, BULLET=.0085 KG
Velocity of the bullet=87 m/s
(10*(.0085*87/10)**2-100*(.0085*87/100)**2)/2
*a. .0246, b. .0382, c. .048, d. .0792, e. .0914
Shall I go on? [YES] n