You have been hired as an expert witness by an attorney for a trial involving a traffic accident. The attorney’s client, the plaintiff in this case, was traveling castbound toward an intersection at 13.0 m/s as measured just before the accident by a roadside speed meter, and as seen by a trustworthy witness. As the plaintiff entered the intersection, his car was struck by a northbound driver, the defendant in this case, driving a car with identical mass to the plaintiff’s. The vehicles stuck together after the collision and left parallel skid marks at an angle of θ = 55.0° north of east, as measured by accident investigators. The defendant is claiming that he was traveling within the 35-mi/h speed limit. What advice do you give to the attorney?
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Chapter 9 Solutions
Physics for Scientists and Engineers with Modern Physics
- A car with mass mc = 1295 kg is traveling west through an intersection at a magnitude of velocity of vc = 9.5 m/s when a truck of mass mt = 1737 kg traveling south at vt = 12.8 m/s fails to yield and collides with the car. The vehicles become stuck together and slide on the asphalt, which has a coefficient of friction of μk = 0.5.Write an expression for the velocity of the system after the collision, in terms of the variables given in the problem statement and the unit vectors i and j. How far, in meters, will the vehicles slide after the collision?arrow_forwardA gymnast jumps straight up, with her center of mass moving at 3.99 m/s as she leaves the ground. How high above this point is her center of mass at the following times? (Ignore the effects of air resistance, and assume the initial height of her center of mass is at y = 0.) t (s) y (m) 0.100 0.200 0.300 0.500arrow_forwardAn object with mass m1 = 3.00 kg is moving along the positive x axis with a speed v1i = 2 m/s straight towards two objects with masses m2 = 2.00 kg and m3 = 4.00 kg, which are initially at rest. When they collide, object 1 comes to rest and object 2 moves away with a speed of v2f = 1.5 m/s at an angle of 50 degrees above the x axis. What is the direction of the velocity of the center of mass of the system comprised of all three objects after the collision? A) Along the x axis B) A an angle of 50 degrees above the x axis C) At an angle of 50 degrees below the x axis D) At an angle > 0 degrees and <50 degrees above the x axis E) At an angle>0 degrees and <50 degrees below the x axis The correct answer is A but I am confused why it is A, if you could explain the justification as to why the answer is option A.arrow_forward
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- A space probe, initially at rest, undergoes an internal mechanical malfunction and breaks into three pieces. One piece of mass ml = 48.0 kg travels in the positive x-direction at 12.0 m/s, and a second piece of mass m2 = 62.0 kg travels in the xy-plane at an angle of 105 at 15.0 m/s. The third piece has mass m3 = 112 kg. (a) Sketch a diagram of the situation, labeling the different masses and their velocities, (b) Write the general expression for conservation of momentum in the x- and y-directions in terms of m1, m2, m3, v1, v2 and v3 and the sines and cosines of the angles, taking to be the unknown angle, (c) Calculate the final x-components of the momenta of m1 and m2. (d) Calculate the final y-components of the momenta of m1 and m2. (e) Substitute the known momentum components into the general equations of momentum for the x- and y-directions, along with the known mass m3. (f) Solve the two momentum equations for v3 cos and v3 sin , respectively, and use the identity cos2 + sin2 = 1 to obtain v3. (g) Divide the equation for v3 sin by that for v3 cos to obtain tan , then obtain the angle by taking the inverse tangent of both sides, (h) In general, would three such pieces necessarily have to move in the same plane? Why?arrow_forwardTwo bumper cars at the county fair are sliding toward one another (Fig. P11.54). Initially, bumper car 1 is traveling to the east at 5.62 m/s, and bumper car 2 is traveling 60.0 south of west at 10.00 m/s. They collide and stick together, as the driver of one car reaches out and grabs hold of the other driver. The two bumper cars move off together after the collision, and friction is negligible between the cars and the ground. a. If the masses of bumper cars 1 and 2 are 596 kg and 625 kg respectively, what is the velocity of the bumper cars immediately after the collision? b. What is the kinetic energy lost in the collision? c. Compare your answers to part (b) from this and Problem 54. Is one answer larger than the other? Discuss and explain any differences you find.arrow_forwardPART 1: A 5.00 kg particle has the xy coordinates (1.20 m, 2.00 m), and a 6.00 kg particle has the xy coordi-nates (0.300 m, 0.750 m). Both lie on a horizontal plane. At what (a) x and (b) y coordinates must you placea 4.00 kg particle such that the center of mass of the three-particle system has the coordinates (0.500 m, 0.900 m)? PART 2: A rope is used to pull a 3.5 kg block at constant speed 6 m along a horizontal oor. The force onthe block from the rope is 7 N and directed = 20 above the horizontal. What are (a) the work done by therope's force, (b) the increase in thermal energy of the block- oor system. PART 3: Draw a labelled gure to explain the idea of turning point in terms of energy.arrow_forward
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