4. In July of 1977, racecar driver David Purley had a horrific crash in which hi

Question

4. In July of 1977, racecar driver David Purley had a horrific crash in which his car's throttle was jammed wide open. meaning his car would only allow the throttle to be completely down. As a result. he crashed into a wall at an amazing 173 km/hr and was decelerated? down to 0 km/hr within a distance of only 0.66 m. 1f we assume his acceleration was constant. calculate the magnitude of the acceleration David experienced during this crash. Express your answer in terms of g?s that is. in terms of the acceleration due to gravity: g=9.81 m/s^2. To date, David?s crash is the most severe g-force ever experienced by a human being who still survived. 5. A bicyclist is finishing his repair of a flat tire when a friend rides by with a constant speed of 3.5 m/s. Two seconds later the bicyclist hops on his bike and accelerates at 2.4 m/s^2 until he manages to catch his friend. a) How much time does it take for the bicyclist to catch his friend? b) How far does he have to travel to catch his friend? c) What is the bicyclists speed when he catches his friend? 6. A simple way to test reaction times is to have someone drop a ruler in between your two fingers and you catch it as quickly as you can. a) If the ruler starts at one end (0 cm). and you catch it with your fingers on the 7.5 cm mark. what is your reaction time? b) 1f the best human reaction times are around 0.10 s, would you be willing to set up a game using the same experiment with a $100 dollar bill, which is about 15 cm In length? The point of the game Is you hold the $100 dollar bill while the Player's has their fingers at the exact middle of the bill. You then drop it. and if the player manages to catch the $100 bill, they get to keep it...if they don?t, they owe you $5. 7. Standing side by side, you and a friend step of a bridge at different times and fall for 1.6 s to the water below. Your friend goes first and you soon follow after your friend has dropped a distance of 2.0 m. a) When your friend hits the water. are you two still separated by 2.0 m? Is it less? Is it more? (No calculation allowed!) b) Verify your answer to a) by calculating the actual separation distance.

Explanation / Answer

initial velocity = Vi = 173 km/hr = 173 km/hr (1000 m/1 km) (1 hour/3600 sec) = 48.1 m/s

final velocity = Vf = 0 m/s

distance travelled = d = 0.66 m

acceleration = a

Using the formula ::

Vf2 = Vi2 + 2 a d

02 = 48.12 + 2 a (0.66)

a = -1752.735 m/s2

a = (-1752.735 /9.8) g

a = -178.85g m/s2

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