Air molecules in a warm room (27°C = 300 K) typically have speeds of about 500 m/s (1,100 mph). Why is it that we are unaware of these fast-moving particles continuously colliding with our bodies? O The density of the warm air is so low that the air molecules tend to miss our bodies. O The size of an air molecule is extremely small, so its momentum and kinetic energy are not efficiently transferred to our bodies when the collisions with a human body occur. O Because the air molecules are everywhere around us they constantly collide with our bodies from all directions. The effect of these collisions tend to cancel out. O The mass of an air molecule is so miniscule that its momentum and kinetic energy are too small to be evident in the collision with a human body. Need Help? Read It

Air molecules in a warm room (27°C = 300 K) typically have speeds of about 500 m/s (1,100 mph). Why is it that we are unaware of these fast-moving particles continuously colliding with our bodies? O The density of the warm air is so low that the air molecules tend to miss our bodies. O The size of an air molecule is extremely small, so its momentum and kinetic energy are not efficiently transferred to our bodies when the collisions with a human body occur. O Because the air molecules are everywhere around us they constantly collide with our bodies from all directions. The effect of these collisions tend to cancel out. O The mass of an air molecule is so miniscule that its momentum and kinetic energy are too small to be evident in the collision with a human body. Need Help? Read It

Physics for Scientists and Engineers: Foundations and Connections

1st Edition

ISBN:9781133939146

Author:Katz, Debora M.

Publisher:Katz, Debora M.

Chapter11: Collisions

Section: Chapter Questions

Problem 50PQ: In a laboratory experiment, an electron with a kinetic energy of 50.5 keV is shot toward another...

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In a laboratory experiment, an electron with a kinetic energy of 50.5 keV is shot toward another electron initially at rest (Fig. P11.50). (1 eV = 1.602 1019 J) The collision is elastic. The initially moving electron is deflected by the collision. a. Is it possible for the initially stationary electron to remain at rest after the collision? Explain. b. The initially moving electron is detected at an angle of 40.0 from its original path. What is the speed of each electron after the collision? FIGURE P11.50
A particle has a momentum of magnitude 40.0 kg m/s and a kinetic energy of 3.40 102 J. a. What is the mass of the particle? b. What is the speed of the particle?
February 3, 2009, was a very snowy day along Interstate 69 just outside of Indianapolis, Indiana. As a result of the slippery conditions and low visibility (50 yards or less), there was an enormous accident involving approximately 30 vehicles, including cars, tractor-trailers, and even a fire truck. Many witnesses said that people were driving too fast for the conditions and were too close together. In this problem, we explore two rules of thumb for driving in such conditions. The first is to drive at a speed that is half of what it would be in ideal conditions. The other is the 8-second rule: Watch the vehicle in front of you as it passes some object such as a street sign, and you should pass that same object 8 seconds later. On a dry road, the 8-second rule is replaced by a 3-second rule. a. Assume vehicles on a slippery interstate highway follow both rules. What is the distance between the vehicles? b. If a driver followed the first rule of thumb, driving at a lower speed, but used the 3-second rule instead of the 8-second rule, what is the distance between the vehicles? How does that distance compare with the visibility on the day of the accident? c. Suppose drivers do not follow either rule of thumb for slippery conditions. What is the distance between vehicles? How does that distance compare with the visibility on that day? d. Suppose a driver was not obeying either rule of thumb when she sees a tractor-trailer that stopped on the highway. She presses on her brakes, locking the wheels, and her car crashes into the truck. Estimate the magnitude of the impulse exerted on her car. e. Estimate the impulse on the car in part (d) had the driver followed both rules of thumb for slippery conditions instead of ignoring them.
In an attempt to produce exotic new particles, a proton of mass mp = 1.67 1027 kg is accelerated to 0.99c (c = 3.00 108 m/s is the speed of light) and crashed into a helium nucleus of mass mHe = 6.64 1027 kg initially at rest. The collision is elastic. a. What is the kinetic energy of the helium nucleus after the collision? b. What is the kinetic energy of the proton after the collision? (In Chapter 39, well learn what Einstein says about making such calculations.)
(a) How fast must a 3000-kg elephant move to have the same kinetic energy as a 65.0-kg sprinter running at 10.0 m/s? (b) Discuss how the larger energies needed for the movement of larger animals would relate to metabolic rates.
If a spacecraft is launched from the Moon at the escape speed of the Earth, how fast will the spacecraft be going when it is very far away from the Moon, ignoring the effects of other celestial bodies?
O A system consists of three particles, each of mass 5.00 g. located at the coners of an equilateral triangle with sides of 30.0 cm. a) Calculate the potential energy of the system. b) Assume the particles are released simultaneously. Describe the subsequent motion of each. Will any collisions take place? Explain. (answer: a) -1.67E-14 J, b) leaving unstated)
Consider the two pucks shown in the figure. As they move towards each other, the momentum of each puck is equal in magnitude and opposite in direction. Given that 1 what are the final speeds of each puck (in m/s), if. _ the kinetic energy of the system is converted to internal energy? 30.0° 30.0 2 i = 4.54 green Vblue = 2.62 × × x m/s x m/s = 11.0 m/s, and m green 'blue is 20.0% greater than m green'
Consider the two pucks shown in the figure. As they move towards each other, the momentum of each puck is equal in magnitude and opposite in direction. Given that Vi, green = 10.0 m/s, and mblue is 15.0% greater than mgreen' what are the final speeds of each puck (in m/s), if the kinetic energy of the system is converted to internal energy? V green 6.87 Vblue= 6.77 30.0 130.0 x m/s x m/s e
Problem 4 134. Astronomy About 65 million years ago an aster- oid struck Earth in the area of the Yucatan Peninsula and wiped out the dinosaurs and many other life forms. Judging from the size of the crater and the effects on Earth, the asteroid was about 10 km in diameter (assumed spherical) and probably had a density of 2.0 g/cm³ (typi- cal of asteroids). Its speed was at least 11 km/s. (a) What is the maximum amount of ocean water (originally at 20 °C) that it could have evaporated? Express your answer in kilograms and treat the ocean as though it were fresh- water. (b) If the water were formed into a cube, how high would it be? (See Tables 14-3 and 14-4 as needed.)
Assume all gases in this problem are ideal. A person is in a closed room (a racquetball court) with V = 438 m hitting a ball (m = 42.0 g) around at random without any pauses. The average kinetic energy of the ball is 2.10 J. (a) What is the average value of v, in (m2/s²)? m²/s² Does it matter which direction you take to be x? O Yes O No (b) Applying the methods of this chapter, find the average pressure on the walls (in Pa). Pa (c) Aside from the presence of only one "molecule" in this problem, what are the main assumptions in the kinetic theory of gases that do not apply here? (Select all that apply.) O the motion of the ball is isotropic O van der Waals forces are not negligible O gravity is negligible O the motion of the ball is in the x-direction only O the collision between the ball and the wall are inelastic
Canadian nuclear reactors use heavy water moderators in which elastic collisions occur between the neutrons and deuterons of mass 2.0 u. Part A What is the speed of a neutron, expressed as a fraction of its original speed, after a head-on, elastic collision with a deuteron which is initially at rest? Express your answer using three decimal places. ?