HOMEWORK SET 3

1. A net force of 200-newtons acts on a 100-kg boulder and a force of the same magnitude acts on a 100-g pebble. Find the acceleration of each.
2. Find the magnitude of the impulse delivered to a soccer ball when a player kicks it with a force of 1250 N. The foot is in contact with the ball for 5.95 milliseconds. Remember, I = F Dt
3. A 92-kg astronaut and a 1200-kg satellite are at rest, relative to the Space Shuttle. The astronaut pushes the satellite, giving it a speed of 0.14 m/s directly away from the Shuttle. A period of time of 7.5 seconds passes when the astronaut smashes into the Shuttle. What was the initial distance between the astronut and the Shuffle?
4. A charging bull elephant with a mass of 5240 kg comes directly toward you at 4.55 m/s. You toss an elastic sphere of mass 0.15 kg at the heffalump with a speed of 7.81 m/s while letting out a diabolic and sinister laugh. When the elastic sphere bounces back toward you, what's its speed?
5. Three uniform meter sticks, each of mass, m, and length 1.0 meter, are placed on the floor as follows; stick 1 lies upon the y-axis starting at 0.0; stick 2 lies upon the x-axis starting at 0.0; stick 3 lies on the x-axis starting at 1.0 m.
a. Find the location of the center of mass of the metersticks.
b. How would the location of the center of mass be affected if the mass of the metersticks were doubled?
6. Convert the following degree angles to radians: Remember, 2 p radians = 360°
a. 30°
b. 45°
c. 90°
d. 180°
7. Find the angular speed (aka angular velocity, or, w) of
a. the minute hand of Big Ben in London, and 360/3600
b. the hour hand of same.

8. The Crab Nebula has a pulsar (pulsating neutron star) embedded in it, which rotates every 33 ms. Find the angular velocity, w, of this pulsar in radians/sec.

9. When a carpenter shuts off his circular saw, the 10.0-inch (25.4 cm) diameter blade slows from 4440 rpm to 0.00 rpm in 2.50 seconds. Find the angular acceleration, a, of the blade.

10. When standing at the top of a tall building, is your angular velocity, w, greater, less, or the same as if you were at sea level?

11. Two kids ride on a merry-go-round Sally is 2.0 meters from the axis of rotation while Sue is 1.5 meters from same. If the merry-go-round completes one rev per 4.5 s,
a. Find the angular velocity, w, of each kid; v = w r
b. Find the linear velocity, v, of each kid

12. A Ferris wheel with a radius of 9.5 m rotates at a constant rate, completing one revolution every 36 seconds. Find the direction and magnitude of a passenger's acceleration...
a. at the top
b. at the bottom

13. Tons of interplanetary dust and debris fall into Earth's atmosphere every day. What is the effect on Earth's Moment of Inertia?

14. Find the rate at which the rotational K.E. Of Earth is decreasing. The “rate” of energy means energy over time, or, Joules/sec = watts. Earth's Moment of Inertia is 0.331 M¿ R¿2, where M¿ = 6 x 1024 kg and R¿ = 6.4 x 106 m. Its period of rotation increases 2.3 x 10-3 seconds every century. (The iconic symbol for “Earth” is ¿).