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Problem 1
A sprinter running a 100 meter race starts at rest, accelerates at constant acceleration with
magnitude A for 2 seconds, and then runs at constant speed until the end.
a) Find the position (relative to the start position) and speed of the runner at the end of the 2
seconds in terms of A.
b) Assume that the runner takes a total of 10 seconds to run the 100 meters. Find the value of
the acceleration A. You can leave your answer in terms of a fraction but clearly indicate the
units.

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

Related questions

A sprinter running a 100-meter race starts at rest, accelerates at constant acceleration with
magnitude A for 2 seconds, and then runs at a constant speed until the end.
a) Find the position (relative to the start position) and speed of the runner at the end of the 2
seconds in terms of A.
b) Assume that the runner takes a total of 10 seconds to run the 100 meters. Find the value of
the acceleration A. You can leave your answer in terms of a fraction but clearly indicate the
units.

To demonstrate the tremendous acceleration of a top fuel dragracer, you attempt to run your car into the back of a dragster thatis "burning out" at the red light before the start of a race.(Burning out means spinning the tires at high speed to heat thetread and make the rubber sticky.)

You drive at a constant speed of toward the stopped dragster, notslowing down in the face of the imminent collision. The dragsterdriver sees you coming but waits until the last instant to put downthe hammer, accelerating from the starting line at constantacceleration, . Let the time at which the dragster starts toaccelerate be .

a- What is , the longest time after the dragster begins toaccelerate that you can possibly run into the back of the dragsterif you continue at your initial velocity?

b- Assuming that the dragster has started at the last instantpossible (so your front bumper almost hits the rear of the dragsterat ), find your distance from the dragster when he started. If youcalculate positions on the way to this solution, choose coordinatesso that the position of the drag car is 0 at . Remember that youare solving for a distance (which is a magnitude, and can never benegative), not a position (which can be negative).

c- Find numerical values for and in seconds and meters for the(reasonable) values (26.8 m/s) and .
Separate your two numerical answers by commas, and give your answerto two significant figures.

Josef is late for a wedding and is speeding down a straight road at 145 km/hr when he passes an officer sitting in a police car parked behind a billboard at the side of the road. Two seconds after Josef's car passes him, the officer accelerates the police car from rest and maintains maximum acceleration of 8.5 km/hr s until he reaches a top speed of 210 km/hr. Eventually the officer gets within 150 m of the speeding vehicle and turns on the flashing lights. Josef sees the lights in his rearview mirror and panics, slamming on the brakes and starting to skid. Josef's car slows down at a rate of 5.5 m/s2. It takes the officer 0.5 seconds to realize what is happening and to move his foot to the brake pedal before he can start to slow down. The police car slows down at a rate of 6 m/s2.

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