kinematics

[inaccensa]

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Two different objects dropped from rest off a 50m cliff. One lands going 30% faster than the other. Both have the same mass. How much more KE does one object have on landing than the other

 

[tn4596]

(1.3v) ^2 = 1.69 v^2
so 69% more kinetic energy.
btw, is this a real question...how does the 2 object have 2 differnt speed, they should have the same speed due to uniform gravity

 

[docntrainin]

That's what I was wondering, how can they have different speeds? Couldn't you just use the mgh = 1/2mv^2. With this in mind, the kinetic energies should be equal right?

 

[geeyouknit]

Drag, maybe? Different surface area?
Strange and irrelevant detail to put in though.

 

[inaccensa]

ahhh, forgot to square the number. It should be due to surface area or something, I was wondering that too.It is a q from kaplan.

 

[neurodoc]

Two different objects dropped from rest off a 50m cliff. One lands going 30% faster than the other. Both have the same mass. How much more KE does one object have on landing than the other

KE depends on mass and velocity ([MV^2]/2) so this is easy to calculate. Assume both objects have the same mass, "M." One travels at V=1, and the second travels at V'=1.33. The first objects KE is Mx1^2/2= M/2 "KE units." The second object's KE is Mx(1.33)^2/2= M/0.8845 "KE units." Do the math to figure out the difference in KE. 🙂