One theory about the destruction of the space shuttle Columbia in 2003 is that o

Question

One theory about the destruction of the space shuttle Columbia in 2003 is that one of its wings had been damaged on liftoff by a chunk of foam insulation that fell off of one of its external fuel tanks. The New York Times reported on June 5, 2003, that NASA engineers had recreated the impact to see if it would damage a mock-up of the shuttle’s wing. “Before last week’s test, many engineers at NASA said they thought lightweight foam could not harm the seemingly tough composite panels, and privately predicted that the foam would bounce off harmlessly, like a Nerf ball.” In fact, the 1.7-pound piece of foam, moving at 531 miles per hour, did serious damage. A member of the board investigating the disaster said this demonstrated that “people’s intuitive sense of physics is sometimes way off.”

(a) Compute the kinetic energy of the foam, and (b) compare with the energy of a 170-pound boulder moving at 5.3 miles per hour (the speed it would have if you dropped it from about kneelevel). (c) The boulder is a hundred times more massive, but its speed is a hundred times smaller, so what’s counterintuitive about your results?

Explanation / Answer

the kinetic energy of the foam is

KE = 1/2 mv^2 = 1/2 * 1.7 pound( 0.45359237 kilograms/ pound) ( 531 mph( 0.44704 meters / second/ mph)^2

=21725.3 J

(b)

KE = 1/2 mv^2 = 1/2 * 170 pound( 0.45359237 kilograms/ pound) ( 5.3 mph( 0.44704 meters / second/ mph)^2

=216.43J

compare

KE1/ KE2 = 21725.3 J/216.43J =100.38

KE1 = 100.38 KE2

(c)

KE = 1/2 mv^2 = 1/2 * (100)1.7 pound( 0.45359237 kilograms/ pound) ( 531/100 mph( 0.44704 meters / second/ mph)^2

=217.25J

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