2. 1D Motion / Kinematics

Beginning from a signpost, you run 60m to the right, then 60m back. The entire trip takes 24 seconds. What is your speed and velocity for the whole trip?

You walk to the right at 3m/s for 8s, then turn around and walk backwards at 2m/s for some unknown time. You end up 16m to the right from where you started. How long did you walk backwards?

If you are driving 85 km/h along a straight road and you look to the side for 2.0 s, how far do you travel during this inattentive period?

A particle at t₁ = ― 2.0 s is at 𝓍₁ = 5.2 cm and at t₂ = 3.4 s is at 𝓍₂ = 8.5 cm. What is its average velocity over this time interval? Can you calculate its average speed from these data? Why or why not?

A bowling ball traveling with constant speed hits the pins at the end of a bowling lane 16.5 m long. The bowler hears the sound of the ball hitting the pins 2.75 s after the ball is released from his hands. What is the speed of the ball, assuming the speed of sound is 340 m/s?

A horse trots away from its trainer in a straight line, moving 38 m away in 7.4 s. It then turns abruptly and gallops halfway back in 1.8 s. Calculate its average speed

On an audio compact disc (CD), digital bits of information are encoded sequentially along a spiral path. Each bit occupies about 0.28 μm. A CD player's readout laser scans along the spiral's sequence of bits at a constant rate of about 1.2 m/s as the CD spins. (a) Determine the number N of digital bits that a CD player reads every second.

(II) Two ships need to arrive at a site in the middle of the ocean at the same time. They start out at the same time from positions equally distant from the arrival site. They travel at different velocities but both go in a straight line. The first ship travels at an average velocity of 20 km/h for the first 600 km, 40 km/h for the next 800 km, and 20 km/h for the final 600 km. The second ship can only sail at constant velocity. What is the magnitude of that velocity?

(II) Digital bits on a 12.0-cm diameter audio CD are encoded along an outward spiraling path that starts at radius R₁ = 2.5 cm and finishes at radius R₂ = 5.8 cm. The distance between the centers of neighboring spiral-windings is 1.6 μm ( = 1.6 x 10⁻⁶ m) .

(a) Determine the total length of the spiraling path. [Hint: Imagine 'unwinding' the spiral into a straight path of width 1.6 μm , and note that the original spiral and the straight path both occupy the same area.]

(II) The position of an object along a straight tunnel as a function of time is plotted in Fig. 2–40. What is its average velocity

(d) between t = 25.0 s and t = 30.0 s

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(II) Every year the Earth travels about 10⁹ km as it orbits the Sun. What is Earth's average speed in km/h?

(II) An airplane travels 1900 km at a speed of 720 km/h, and then encounters a tailwind that boosts its speed to 990 km/h for the next 2700 km. What was the total time for the trip? What was the average speed of the plane for this trip? [Hint: Does Eq. 2–12d apply?]