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# momentum and velocity

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1. Thoroughbred horse are among the fastest horses in the world and are used in famous racing events such as the Kentucky Derby. The mass of a thoroughbred is about 500 kg. If a horse with this mass is galloping with a momentum of 8.22*10^3 kg.m/s, what is its speed?
2. A pitcher is a professional baseball game throws a fastball, giving the baseball a momentum of 5.83 kg.m/s. Given that the baseball has a mass of 0.145 kg, what is its speed?
3. The maximum speed measured for a golf ball is 273 km/h. If a golf ball with a mass of 47 g has a momentum of 5.83 kg. m/s, the same as that of the baseball in the previous problem, what would its speed be? How does this compare to the golf ball's maximum measured speed?
4. The World solar challenge in 1987 was the first car race in which all the vehicles were solar powered. The winner was GM sunraycer, which has a mass of 177.4 kg, not counting the driver's mass. Assume that the driver has a mass of 61.5 kg, so that the total momentum of the car and driver was 4.416* 10^3 kg.m/s. What was the card's speed in m/s and km/h?
5. Although larger than the Atlantic walrus, the Pacific walrus can swim with a speed of about 9.7m/s. If the momentum of a swimming walrus is 1.07 x 10^4 kg.m/s, what is its mass?
6. The lightest pilot drive airplane even built was Baby Bird. Suppose the Baby Bird moves along the ground without a pilot at a speed of 88.0 km/h. Under these circumstances the momentum of the empty plane would be only 2790 kg.m/s. What is the mass of the plane?
7. The most massive automobile to have been manufactured on a regular basis was the Russian made Z il-41047. If one these cars were to move at just 8.9 m/s, its momentum would be 2.67 x 10^4 kg. m/s. Use this information to calculate the mass of a Zil-41047.
8. The brightest, hottest, and most massive stars are the brilliant blue stars designated as spectral call O. As is the case of all stars, class O stars move with speeds that are measured in km/s.
a. If a class O star moves with a speed of 255 km/s and has a momentum of 8.62 x 10^36 kg.m/s, what is the star's mass?
b. A class O star typically has a mass of at least 10 solar masses. Express the mass calculated in part a in terms of solar masses.
9. The shinkansen, Japan's high speed bullet train, consists of several different versions of trains that have been in service since 1963. The 100-series trains consist of 16 steel cars that have a combined mass of 9.25 *10^5 kg. The top speed of a regular 100-series train is 220 km/h. What would be the momentum of one of these trains?
10. The 300-series shinkansen trains consist of 16 aluminum cars with a combined mass of 7.10* 10^5 kg. The reduction in mass from the 100-series enables the 300 series trains to reach a top speed of 270 km/h. What is the momentum of one of these trains at its top speed? Is the momentum of a 300-series greater or less than the momentum of 100-series train traveling at its top speed?
11. The largest animal ever to have lived on Earth is the blue whale. Consider a blue whale with a mass of 1.46*10^5 kg and a top swimming speed of 24 km/h. What is the momentum of this whale at this speed?
12. The current holder of the men's world record for running 200m is Michael Johnson, who in 1996 ran 200.0m in 19.23 s. Johnson's mass at the time of his record breaking run was about 77 kg. What was his momentum at his average speed?
13. An athlete with a mass of 73.0 kg runs with a constant forward velocity of 1.50 m/s. What is the athlete's momentum?
14. If a car with a mass of 925 kg has the same momentum as the athlete in the previous question, what is the car's speed?
15. Jenny has a mass of 35.6 kg and her skateboard has a mass of 1.3 kg. What is Jenny and her skateboard's momentum if they are going 9.50 m/s.

https://brainmass.com/physics/stars/momentum-and-velocity-142726

#### Solution Summary

It shows how to calculate the momentum. The solution is detailed and was rated '5/5' by the student who posted the questions.

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## Physics Questions

1. (a) What is the momentum of a 1.20 x 10^4 kg garbage truck moving at 30.0 m/s? (b) At what speed would an 8.00 kg trash can have the same momentum?

2. One hazard of space travel is debris left by previous missions. There are several thousand masses large enough to detect by radar orbiting the earth, but there are far greater numbers of very small masses, such as flakes of paint. Calculate the force exerted by a 0.100 mg chip of paint that strikes a space shuttle window at a relative speed of 4000 m/s, given the collision lasts 6.00 x 10^(-8) s. Such a collision chipped the window of the ill-fated Challenger in June 1983, causing \$50,000 of damage.

3. A 0.450 kg hammer is moving horizontally at 7.00 m/s when it strikes a nail and comes to rest after driving it 1.00 cm into a board. (a) Calculate the duration of the impact. (b) What was the average force exerted on the nail?
Note: There are (at least) two strategies here. One is to assume constant acceleration over the 1-cm distance and determine the time using the equations for constant acceleration. From that, you can find the average force. However, a more "relevant" strategy, in terms of what we have been learning, is to first use the work-energy principle to find the average force. Then use the impulse-momentum principle to find the duration of impact.

4. It is possible for the velocity of a rocket to be greater than the exhaust velocity of the gases it ejects. When that is the case, the gas velocity and momentum are in the same direction as the rocket's. How does the rocket still obtain thrust by ejecting the gases?

5. Water from a fire hose is directed horizontally against a wall at a rate of 50.0 kg/s and a speed of 42.0 m/s. Calculate the force exerted on the wall, assuming the water's horizontal momentum is reduced to zero.

6. Train cars are coupled together by being bumped into one another. Suppose two loaded train cars are moving toward one another, the first having a mass of 150,000 kg and a velocity of 0.300 m/s, and the second having a mass of 110,000 kg and a velocity of -0.120 m/s. What is their final velocity?

7. A 0.240 kg billiard ball moving at 3.00 m/s strikes the bumper and bounces straight back at 2.40 m/s (80% of the original speed.) The collision lasts 0.0150 s. (a) Calculate the average force exerted on the ball by the bumper. (b) How much kinetic energy in joules is lost during the collision? (c) What percent of the original energy is left?

8. Two cars collide at an icy intersection and stick together afterward. The first car has a mass of 1200 kg and was approaching at 8.00 m/s due south. The second car has a mass of 850 kg and was approaching at 17.0 m/s due west. (a) Draw arrows representing the momentum vector of each car, and draw an arrow representing the resultant (vector sum) of these two. Label each arrow with its magnitude in kg-m/s. (Make this a clear diagram, with arrows at least 3 inches long. Make the relative length of the arrows accurate.) (b) Calculate the final velocity of the cars. (Magnitude and direction.) (c) How much kinetic energy is lost in the collision? (This energy goes into deformation of the cars.)

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