Concept explainers
You have a great job working at a major league baseball stadium for the summer! At this stadium, the speed of every pitch is measured using a radar gun aimed at the pitcher by an operator behind home plate. The operator has so much experience with this job that he has perfected a technique by which he can make each measurement at the exact instant at which the ball leaves the pitcher’s hand. Your supervisor asks you to construct an algorithm that will provide the speed of the ball as it crosses home plate, 18.3 m from the pitcher, based on the measured speed vi of the ball as it leaves the pitcher’s hand. The speed at home plate will be lower due to the resistive force of the air on the baseball. The vertical motion of the ball is small, so, to a good approximation, we can consider only the horizontal motion of the ball. You begin to develop your algorithm by applying the particle under a net force to the baseball in the horizontal direction. A pitch is measured to have a speed of 40.2 m/s as it leaves the pitcher’s hand. You need to tell your supervisor how fast it was traveling as it crossed home plate. (Hint: Use the chain rule to express acceleration in terms of a derivative with respect to x, and then solve a differential equation for v to find an expression for the speed of the baseball as a function of its position. The function will involve an exponential. Also make use of Table 6.1.)
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Chapter 6 Solutions
Physics for Scientists and Engineers
- I don't understand how to do this. Now let's see what we can tell from an equation for position:x(t) = 6t^2 + 4.2t + 9What is the object's initial position? Assume each term has units of meters, and that time is in secondsarrow_forwardA man starts from home (x = 0), over about 30 seconds, he accelerates towards a steady state of 4 m/s according to the function: v(t) = 4(1 – e-t/(30 s) m/s and his whole ride lasts 1000 seconds (about 17 minutes). a. How far did he travel?b. What would the distance covered by the man be if the whole trip was travelled at a steady state speed of 4m/s?c. How less/more has the man travelled in part (a) as compared to part (b)?arrow_forwardA particle of mass m has a time-dependent position vector r(t) = (Rcos(ωt),Rsin(ωt),αt) in Cartesian coordinates, where R, ω and α are positive constants. What are the physical dimensions of R, ω and α? Show that the speed of the particle is constant. Does it mean that the acceleration is zero? Justify.arrow_forward
- After a ball rolls off the edge of a horizontal table at time t = 0, its velocity as a function of time is given by v=1.2i9.8tj where v is in meters per second and t is in seconds. The balls displacement away from the edge of the table, during the time interval of 0.380 s for which the ball is in flight, is given by r=00.3803vdt To perform the integral, you can use the calculus theorem [A+Bf(x)]dx=Adx+Bf(x)dx You can think of the units and unit vectors as constants, represented by A and B. Perform the integration to calculate the displacement of the ball from the edge of the table at 0.380 s.arrow_forwardCalculate the result for each of the following cases using the correct number of significant figures. a. 3.07670 10.988 b. 1.0093 105 9.98 104 c. 5.44231064.008103arrow_forwardIn Jules Vernes novel, Twenty Thousand Leagues Under the Sea, Captain Nemo and his passengers undergo many adventures as they travel the Earths oceans, a. If 1.00 league equals 3.500 km, find the depth in meters to which the crew traveled if they actually went 2.000 104 leagues below the ocean surface. b. Find the difference between your answer to part (a) and the radius of the Earth, 6.38 106 m. (Incidentally, author Jules Verne meant that the total distance traveled, and not the depth, was 20,000 leagues.)arrow_forward
- Mario rides his motorcycle in going to school. He drives at an average speed of 30 kilometers per hour. The distance between his house and the school is 15 kilometers. Every time he sees his best friend Jessica walking on the road, he invites her for a ride and lowers his speed. On the other hand, he increases his speed when he wakes up late for school. a) If x represents the time it takes Mario to drive to school with the given distance of 15 kilometers, how will you represent the relationship of his speed (y) versus the time (x)?arrow_forward2. A mouse enters a basement room through a hole in one of the walls. It then travels through the room before running out through a hole in another wall. The mouse is filmed by a surveillance camera on the ceiling. A physics student analyzes the recording and sets up the equations for movement to the mouse. The student uses x and y axes along the two walls with holes in them. The x and y positions as a function of time are x (t) = −0.10 m / s2 · t2 + 1.8 m / s · t y (t) = −0.20 m / s2 · t2 + 2.0 m / s · t + 3.0 m (a) Draw the motion of the mouse in the xy plane. For example, you can plot the position every second. (b) Determine the speed and acceleration of the mouse after 3.0 s. Draw the vectors in the figure in (a). (c) When does the mouse run out through the second hole?arrow_forwardAs a city planner, you receive complaints from local residents about the safety of nearby roads and streets. One complaint concerns a stop sign at the corner of Pine Street and 1st Street. Residents complain that the speed limit in the area (55 mph)(55 mph) is too high to allow vehicles to stop in time. Under normal conditions this is not a problem, but when fog rolls in visibility can reduce to only 155 ft.155 ft. Since fog is a common occurrence in this region, you decide to investigate. The state highway department states that the effective coefficient of friction between a rolling wheel and asphalt ranges between 0.8420.842 and 0.941,0.941, whereas the effective coefficient of friction between a skidding (locked) wheel and asphalt ranges between 0.5500.550 and 0.754.0.754. Vehicles of all types travel on the road, from small VW bugs weighing 1170 lb1170 lb to large trucks weighing 8670 lb.8670 lb. Considering that some drivers will brake properly when slowing down and others will…arrow_forward
- Vx=525 m/s 2. A rifle is aimed horizontally shoulder height (1.5 meters above the ground) at a target bulls eye 700 meters away. The bullet leaves the gun with a muzzle velocity of 1000 m/s. a. Fill out the chart and find how much time it takes the bullet to reach the target. X Dimension Xo = 0 X = Vox= ax = t= Y Dimension Yo = 15 700m Y = 1000 MIS| Voy = U m/s m/ ay = 9₁.8 m/s +=0% b. How far vertically below the bullseye does the bullet hit the target? If the vertical drop is *more* than 1.5m, where on the ground does it hit? Y=090- Aarrow_forwardGiven that the acceleration vector is a(t)=(−16cos(−4t))i+(−16sin(−4t))j+(1t)k, the initial velocity is v(0)=i+k, and the initial position vector is r(0)=i+j+k, compute: A. The velocity vector v(t) B. The position vector r(t)arrow_forwardYou are observing the poles along the side of the road as described in the opening storyline of the chapter. You have already stopped and measured the distance between adjacent poles as 40.0 m. You are now driving again and have activated your smartphone stopwatch. You start the stopwatch at t 5 0 as you pass pole #1. At pole #2, the stopwatch reads 10.0 s. At pole #3, the stopwatch reads 25.0 s. Your friend tells you that he was pressing the brake and slowing down the car uni- formly during the entire time interval from pole #1 to pole #3. (a) What was the acceleration of the car between poles #1 and #3? (b) What was the velocity of the car at pole #1? (c) If the motion of the car continues as described, what is the number of the last pole passed before the car comes to rest?arrow_forward
- Physics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage LearningPhysics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning