Measure Your Reaction Time Here's something you can try at home-an experiment to measure your reaction time. Have a friend hold a ruler by one end, letting the other end hang down vertically. At the lower end, hold your thumb and index finger on either side of the ruler, ready to grip it. Have your friend release the ruler without warning. Catch it as quickly as you can.If you catch the ruler 6.0cmfrom the lower end, what is your reaction time?Express your answer using two significant figures.

After a long and grueling race, two cadets, A and B, are coming into the finish line at the Marine Corps marathon. They move in the same direction along a straight path; the position-versus-time graphs for the runners are shown in Figure P2.7 for a minute near the end of the race. a. At time t1 is the speed of cadet B greater than, less than, or equal to the speed of cadet A? b. At time t2, is cadet B speeding up, slowing down, or moving with constant speed? c. From time t = 0 to time t = 60 s, is the average speed of cadet B greater than, less than, or equal to the average speed of cadet A? Explain.

Two thin rods are fastened to the inside of a circular ring as shown in Figure P2.42. One rod of length D is vertical, and the other of length L makes an angle with the horizontal. The two rods and the ring lie in a vertical plane. Two small beads are free to slide without friction along the rods. (a) If the two beads are released from rest simultaneously from the positions shown, use your intuition and guess which bead reaches the bottom first. (b) Find an expression for the time interval required for the red head to fall from point to point in terms of g and D. (c) Find an expression for the time interval required for the blue bead to slide from point to point in terms of g, L, and . (d) Show that the two time intervals found in parts (b) and (c) are equal. Hint: What is the angle between the chords of the circle and ? (e) Do these results surprise you? Was your intuitive guess in part (a) correct? This problem was inspired by an article by Thomas B. Greenslade, Jr., Galileos Paradox, Phys. Teach. 46, 294 (May 2008). Figure P2.42

An ice sled powered by a rocket engine sum from rest on a large frozen lake and accelerates at + 40 ft/s2. After some time t1, the rocket engine is shut down and the sled moves with constant velocity v for a time t2. If the total distance traveled by the sled is 17 500 ft and the total time is 90 s. find (a) the times t1 and t2 and (b) the velocity v. At the 17 500-ft mark, the sled begins to accelerate at 20 ft/s2. (c) What is the final position of the sled when it comes to rest? (d) How long does it take to come to rest?

A basketball player dribbles the ball while running at a constant speed straight across the court. Think about the velocity and acceleration of the ball and then sketch a motion diagram for the ball. Explain how you arrived at your sketch.

Emily challenges her husband, David, to catch a 1 bill as follows. She holds the bill vertically as in Figure P2.67, with the center of the bill between David's index finger and thumb. David must catch the bill after Emily releases it without moving his hand downward. If his reaction time is 0.2 s, will he succeed? Explain your reasoning. (This challenge is a good trick you might want to try with your friends.) Figure P2.67

You slam on the gas of your racecar and you accelerate at 12 m/s2 from rest to a final velocity of 48 m/s How far will you travel during this acceleration. There IS enough information to find the answer, use your tools.

A race car moves such that its position fits the relationship x = (6.0 m/s)t + (0.80 m/s3)t3 where x is measured in meters and t in seconds. (a) A plot of the car's position versus time is which of the following? (b) Determine the instantaneous velocity of the car at t = 3.7 s, using time intervals of 0.40 s, 0.20 s, and 0.10 s. (In order to better see the limiting process keep at least three decimal places in your answer.) (c) Compare the average velocity during the first 3.7 s with the results of part (b). The average velocity of m/s is  ---Select--- much less than about the same as much greater than the instantaneous velocity

Two motorcycles are at rest and separated by 24.5ft. They start simultaneously in the same direction, the one in the back having an acceleration of 3.00 ft/sec2 and the one in the front with an acceleration of 2.00 ft/sec2. How long does it take for the faster cycle to overtake the slower? How far does the faster machine go before it catches up? How fast is each cycle going at this time?

A cork bobs up and down in a lake. The distance from the bottom of the lake to the center of the cork at time t>=0 is given by s(t)= 25+cos(pi t), where s(t) is in feet and t Is in seconds. During what time interval is the cork rising. Draw pictures as well