A group of friends on a hike get tired and decide to ride a perfectly uniform 5-m log down a river to help them get closer to their starting point. Paige whose mass is 40-Kg sits a half meter from the front and Kenny at 60-Kg sits a quarter of a meter from the back. Finally, Ed estimates the log’s mass to be 1,000-Kg and knows that he should sit 3-m from the back in order to keep the Center of  Mass exactly in the middle of the log for a smoother ride. What is Ed’s mass?

4. Object A, whose center is at (2.0m, 2.0m) has a mass of 40 kg. Object B has its center at (10m, 4.0m) and has a mass of 30 kg. What is the x component of their center of mass in m? a) 2.9 6. b) 5.4 B c) 6.1 4. d) 6.3 A e) 6.7 2 8. 10 12 x (m) 6. 2) (w)m)

From 1946 through 1958, Col. John Stapp headed the U.S. Air Force Aero Medical Laboratory's studies of the human body's ability to tolerate high accelerations during plane crashes. Conventional wisdom at the time indicated that a plane's negative acceleration should not exceed 180 m/s2 (18 times gravitational acceleration, or 18g). Stapp and his colleagues built a 700-kg "Gee Whiz" rocket sled, track, and stopping pistons to measure human tolerance to high acceleration. Starting in June 1949, Stapp and other live subjects rode the sled. In one of Stapp's rides, the sled started at rest and 360 m later was traveling at speed 67 m/s when its braking system was applied, stopping the sled in 6.0 m. He had demonstrated that 18g was not a limit for human deceleration.   Find the time interval for Stapp and his sled to stop as their speed decreased from 67 m/s to zero.

Flying Circus of Physics On August 10, 1972, a large meteorite skipped across the atmosphere above the western United States and western Canada, much like a stone skipped across water. The accompanying fireball was so bright that it could be seen in the daytime sky and was brighter than the usual meteorite trail. The meteorite's mass was about 3.7 × 106 kg; it's speed was about 14 km/s. Had it entered the atmosphere vertically, it would have hit Earth's surface with about the same speed. (a) Calculate the meteorite's loss of energy (as a positive number, in joules) that would have been associated with the vertical impact. (b) Express the energy as a multiple of the explosive energy of 1 megaton of TNT, which is 4.2 × 1015 J. (c) The energy associated with the atomic bomb explosion over Hiroshima was equivalent to 13 kilotons of TNT. To how many Hiroshima bombs would the meteorite impact have been equivalent? (a) Number (b) Number Units Units (c) Number Units

There is a large crater in Arizona called Meteor Crater. It is estimated that it was formed about 20,000 years ago by a meteorite that had a mass of about 5 x 10^10 kg and was traveling at a speed of 7.5 km/sec. How fast could this meteorite have hit the Earth (whose mass is 6 x 10^24 kg) if we assume a head-on collision?

11.

15. Researchers studying BIO the possible effects of "heading" a soccer ball- hitting it with the head- use a force plate to mea- sure the interaction force between a ball and a hard surface. Figure P8.15 shows smoothed data of the force when a 430 g soccer ball is fired hori- Fx (N) 3000 2000 1000 0 0 2 FIGURE P8.15 4 6 8 t (ms) zontally at the force plate with a speed of 16 m/s. With what speed does the ball rebound from the plate?

1.You are holding a shopping basket at the grocery store with two 0.56-kg cartons of cereal at the left end of the basket. The basket is 0.71 m long. Where should you place a 1.8-kg half gallon of milk, relative to the left end of the basket, so that the center of mass of your groceries is at the center of the basket?Explain and labled the problem.

A spaceship with fuel is initially at rest at point CG.  Fuel is ejected at the back to propel the payload to the forward direction.  After a long time, the total fuel ejected out has a mass of 1e6 pounds, and center of gravity moving backward at 20 m/s.  The forward speed of the payload relative to CG is 150 m/s.  The payload mass is _____ pounds.