In 1964, after the 1250-kg jet-powered car Spirit of America lost its parachute

Question

In 1964, after the 1250-kg jet-powered car Spirit of America lost its parachute and went out of control during a run at Bonneville Salt Flats, Utah, it left skid marks about 8 km long. (This earned a place in the Guinness Book of World Records for longest skid marks.)

1)(a) If the car was moving initially at a speed of about 711 km/h, and was still going at about 296 km/h when it crashed into a brine pond, estimate the coefficient of kinetic friction ? k.

2)(b) What was the kinetic energy of the car 39 s after the skid began? (in MJ)

Explanation / Answer

A )

here

v = 296 km/h = 82.22 m/s

u = 711 km/h = 197.5 m/s

here by using thrid equation of motion

v^2 - u^2 = 2* a* s

82.22^2 - 197.5^2 = 2 * a * 8000

a = 32246.13 / 16000

a = -2.01 m/s^2

the -ve sign indicate the decleration

so by using

s = u^2 / 2 * a * uk

uk= 197.5^2 / 2 * 2.01 * 8000

uk= 1.21

the cofficient of kinetic friction is 1.21

B)

by using the first equation of motion

v = u +at

v = 197.5 - 2.01*39

v = 119.11 m/s

so the kinetic energy is

KE = 0.5 * m * v^2

KE = 0.5 * 1250 * 119.11^2

KE = 8866995.05 J

KE = 8.87 MJ

so the kinetic energy of te car after 39 sec is 8.87MJ

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