What is the Kinetic Energy of a 3000lb Car Traveling at 60mph?

AI Thread Summary
The kinetic energy of a 3000 lb car traveling at 60 mph can be calculated using the formula KE = 1/2 * mass * velocity^2. To find the mass in kilograms, convert 3000 lbs to mass using the acceleration due to gravity. The velocity must also be converted from miles per hour to feet per second for consistency in units. The final calculation yields a kinetic energy of approximately 360,745 foot-pounds. Understanding the distinction between pounds as force and mass is crucial for accurate calculations.
mbm
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Homework Statement



what is the kinetic energy of a 3000lb car traveling at a 60mph (pounds are not units of mass)

Homework Equations


KE=1/2* mass * velocity ^2


The Attempt at a Solution



pounds are the units of force but to calculate the mass I am missing some data unless I'm supposed to use gravity...
 
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You're confused because pounds are units of mass.
 
There is the the pound for force and the pound for mass.

1 pound of mass is about 0.454 Kilograms

1 pound of force is (0.454*g) Newton where g is the acceleration of gravity

Whether you take it to be pound of force or pound of mass you ll end up with the same result. (If you take it to be pound of force after you convert it to Newtons you ll have to divide by g to get the mass in kilograms)
 
mbm said:

Homework Statement



what is the kinetic energy of a 3000lb car traveling at a 60mph (pounds are not units of mass)

Homework Equations


KE=1/2* mass * velocity ^2


The Attempt at a Solution



pounds are the units of force but to calculate the mass I am missing some data unless I'm supposed to use gravity...

You have to convert 3000lbs to kilograms and 60 mph to meters per second (m/s)
 
thnx! I now understand!
 
alfredo24pr: I disagree. You are given W = 3000 lbs = mass of car * g
and V = 60 mph. m = 3000 / 32.2 lb-s^2/ft v = 60 * 5280 / 3600 ft/s

KE = (1/2) m*v^2 = (0.5) * (3000/32.2) *[60*5280/3600]^2
KE = 360,745 ft-lbs
 

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