Four railroad cars, each of mass 2.50 × 104 kg, are coupled together and coasting along horizontal tracks at speed vi toward the south. A very strong but foolish movie actor, riding on the second car, uncouples the front car and gives it a big push, increasing its speed to 4.00 m/s southward. The remaining three cars continue moving south, now at 2.0 m/s. (a) Find the initial speed of the four cars. (b) By how much did the potential energy within the body of the actor change? (c) State the relationship between the process described here and the process in Problem 13.
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Chapter 9 Solutions
Bundle: Physics for Scientists and Engineers with Modern Physics, Loose-leaf Version, 10th + WebAssign Printed Access Card for Serway/Jewett's Physics for Scientists and Engineers, 10th, Multi-Term
- While driving to work one day, I was holding my coffee mug in my left hand while changing the radio station with my right hand. Then my cell phone rang, so I placed the mug on the flat part of my dashboard. Then, believe it or not, a deer ran out of the woods and onto the road right in front of me. Fortunately, my reaction time was zero, and I was able to stop from a speed of 17 m/s in a mere 50 m, just barely avoiding the deer, without the coffee mug sliding. The mug (with coffee) had a mass of 550 g, and the mass of the deer was 150 kg. Part A What is the minimum possible value of the coefficient of static friction between the mug and the dashboard? Hg =arrow_forwardIo, a satellite of Jupiter, is the most volcanically active moon or planet in the solar system. It has volcanoes that send plumes of matter over 500 km high. Due to the satellite's small mass, the acceleration due to gravity on Io is only 1.81 m/s2and Io has no appreciable atmosphere. Assume that there is no variation in gravity over the distance traveled. a)What must be the speed of material just as it leaves the volcano to reach an altitude of 380 km? b)If the gravitational potential energy is zero at the surface, what is the potential energy for a 33 kg fragment at its maximum height (500 km) on Io? c)How much would this gravitational potential energy be if it were at the same height (500 km) above earth?arrow_forwardWhen an object accelerates at 9.8 m/s2 (or 32 ft/s2), we say it accelerates with 1 g. This is true whether the object is falling under gravity, or due to something else. Using the constant-acceleration approximation, determine how many g's are involved in a football kickoff. The ball is initially at rest on the tee. After being in contact with the kicker’s foot for only 8 ms, it leaves the kicker’s foot at 118 ft/s. Round the final answer to the nearest whole number.arrow_forward
- a (m/s?) В 2. SpaceX engineers is planning to build a 2-stage rocket which has a-t graph as shown. By their design, the first stage A will burn out after 20 seconds and then the second stage B will A 30 22 ignite. Plot the v-t and s-t graphs which describe the two-stage motion of the missile for 0st< 30s. t (s) 20 30arrow_forwardA biomechanics forensics expert is attempting to determine the events that led to an automobile accident in which one car rear-ended another. The two cars were originally travelling in the same direction. Car A was traveling at a speed of 42 km/hr when it was struck by Car B, which was traveling at 65 km/hr. Following the collision, the two cars became entangled and continued to travel as one unit with a speed of 53 km/hr. From an interview with the driver of Car A, the forensics expert learned that the mass of Car A is 575 kg. What is the mass of Car B (in kg)? Express your answer in kilograms to one decimal place (do not include units in your answer). Your Answer:arrow_forwardA student pushes a 12-kg block on a frictionless, horizontal surface. If the block is initially at rest, what is the speed of the block after the student pushes the block for 5 seconds with an acceleration of 2.0 m/s/s? O 2.0 m/s 6.0 m/s 10 m/s 60 m/sarrow_forward
- In the winter sport of bobsledding, athletes push their sled along a horizontal ice surface and then hop on the sled as it starts to careen down the steeply sloped track. In one event, the sled reaches a top speed of 9.2 m/sm/s before starting down the initial part of the track, which is sloped downward at an angle of 9.0 ∘∘.arrow_forwardI was standing on the side of a 10-m foot bridge, holding a ball while watching a car approaching the bridge at uniform speed. When the car was 15 meters away from where I was standing, the ball that I was holding slipped in my hand and the car arrived at the bridge when the ball hit the ground. What was the speed of the train? ( Assume that the final velocity of the ball is NOT zero)arrow_forwardA friend claims that her car can accelerate from a stop to 60 mi/h (26.8 m/s) in 7.5 s, but the speedometer is broken. You decide to test her claim by riding with her, and you bring along a small metal washer, a short length of string, a protractor, and a pen that can write on glass. Sitting in the passenger seat, you tie the washer to one end of the string and then let the string-washer combination hang straight down by rolling up the passenger-door window to pinch the free end of the string. While the car is stationary, you draw a line on the window alongside the vertical string. ▬▬ Review How large is the angle the string makes with the line you drew if the car accelerates at the rate your friend claims? 0= ΠΕ| ΑΣΦ Submit Part B Request Answer ? IVE ΑΣΦ 5 P Pearson If an identical washer does not slide on the horizontal dashboard while this is happening, what is the ratio of the frictional force to the gravitational force exerted on this washer? 11 of 22 ? Copyright © 2023 Pearson…arrow_forward
- A student launches a small rocket which starts from rest at ground level. At a height of h = 1.8 km the rocket reaches a speed of vf = 342 m/s. At that height the rocket runs out of fuel, so there is no longer any thrust propelling it. Take the positive direction to be upward in this problem B: After the rocket's engine turns off at a height of h = 1.8 km, it continues to move upward due to the velocity that it reached. What is the rocket's acceleration, in meters per second squared, during the period from engine shutoff until it returns to the ground? Ignore air resistance. C: Calculate the maximum height, in meters above ground level, that the rocket reaches.arrow_forwardAn object has a velocity (4.69 m/s)i + (-4.4 m/s)j + (4.73 m/s)k. In a time of 5.5 s its velocity becomes (-2.22 m/s)i + (0.00 m/s)j + (4.73 m/s)k. 1) If the mass of the object is 3.31 kg, what is the magnitude of the net force on the object, in N, during the 5.5 s? Assume the acceleration is constant.arrow_forwardIn a cathode ray tube, electrons are accelerated from rest by a constant electric force of magnitude 6.40 x 10-17 N during the first 2.70 cm of the tube's length; then they move at essentially constant velocity another 45.0 cm before hitting the screen. Find the speed of the electrons when they hit the screen.arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning