1 A cyclist moves at a constant speed of 15 mi/h. Ex- press the speed in units of ft/s.

1 A cyclist moves at a constant speed of 15 mi/h. Ex- press the speed in units of ft/s.
2 How long is required to travel 300 km along a freeway at a constant speed of (a) 50.0 km/h; (b) 60.0 km/h?
3 Light travels at a constant speed of 3.00 3 108 m/s, whereas sound travels through the air at a constant speed of 340 m/s. (a) How long does it take for light to travel from a
lightning stroke to an observer 1.00 km away? (b) How long after the flash is seen is the thunder pro-
duced by the lightning heard? 4 The driver of a car is initially moving at a constant
speed of 72.0 km/h when a traffic light turns red. If 0.500 s reaction time is required before the brakes can be applied, what is the distance in meters traveled by the car before it begins to slow down?
5 A person on earth communicating with an astronaut on the moon asks a question. How long must the per- son on earth wait for a response if the astronaut an- swers 1.00 s after the message is received? The moon is 3.84 3 105 km from the earth, and the speed of ra- dio waves is 3.00 3 108 m/s.
6 External stimuli are communicated to the brain by means of electrical signals propagating along nerve cells at a speed of approximately 30 m/s. Similarly, electrical messages are sent at the same speed from the brain along nerve cells to the muscles. Reflex ac- tions are controlled by a relatively simple nerve circuit from a muscle to the spine and back to the muscle. Es- timate the reflex time for a stimulus at the knee.
7 The world record in the 100 yard dash is 9.1 s. Esti- mate the world record in the 100 m dash.
Average speed 8 Compute the average speed in m/s of a runner who
completes a mile in 4.00 min. 9 Blood circulating from the heart to the hands and back
to the heart travels a distance of about 2.0 m in 40 s. Find the average speed of the blood.
10 You drive from Los Angeles to Portland, a distance of 1.6 3 103 km, in 30 h, including stops. What steady speed would have allowed you to arrive at the same time if you had driven at this speed nonstop?
11 During 5 successive 1.00 min intervals, a runner moves at the following constant speeds: 0.400 km/min, 0.240 km/min, 0.160 km/min, 0.160 km/min, and 0.320 km/min. Compute the total dis- tance traveled and the average speed.
12 A tortoise and a hare race over a course 1.00 km long. The tortoise moves at a constant speed of 2.00 m/s. The hare moves at a speed of 10.0 m/s for 60.0 s, rests for 10.0 min, and continues at 10.0 m/s for 40.0 s. (a) Sketch s versus t for both the tortoise and the hare
on the same graph. (b) Who wins the race? (c) What is the hare’s average speed?
Instantaneous speed 13 A plane accelerates down a runway. Markers beside
the runway are 10.0 m apart. The plane moves be- tween two adjacent markers in 0.200 s. Estimate the instantaneous speed of the plane as it passes the first marker.
14 By analyzing a multiflash photograph of a golfer hit- ting a golf ball, one finds that the head of the club trav- els 50.0 cm in 0.0100 s, just before it strikes the ball. Find the approximate instantaneous speed of the club head at the instant of contact.
15 Let s 5 ct3, where c 5 1.0 m/s3. Compute the average speed over the time intervals Dt1 5 1.0 3 10]1 s, Dt2 5 1.0 3 10]2 s, and Dt3 5 1.0 3 10]3 s, with all time in- tervals starting at the time t 5 1.0000 s. What is the in- stantaneous speed at t 5 1.0000 s?
16 Paradoxes relating to the nature of motion were for- mulated by the ancient Greeks. The paradoxes were not resolved because the Greeks had no clear under- standing of concepts like instantaneous speed. One of Zeno’s paradoxes can be stated as follows: a runner wishing to run 100 meters must first cover half that distance. But before he can cover the 50 meters, he must first travel 25 meters, and so on. It is clear that before the runner can travel 100 meters, or any finite distance, he must first move through an infinite num- ber of shorter distances, and this he can never do in a finite time. Resolve this paradox.