Kinetic Energy Ratio: Objects Moving at 5m/s & 25m/s

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The discussion focuses on calculating the kinetic energy ratio of two identical objects moving at speeds of 5 m/s and 25 m/s using the formula KE = 1/2 mv^2. The kinetic energies are determined to be 12.5m and 312.5m, leading to a ratio of 25:1 when comparing the two. Participants emphasize the importance of squaring the velocities in the ratio calculation, confirming that the ratio of kinetic energies is equivalent to the square of the ratio of their speeds. There is some confusion regarding the relevance of potential energy, which is clarified as unrelated to this specific problem. Ultimately, the correct kinetic energy ratio is established as 25:1.
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it reads, '' two identical objects move with speeds of 5m/s and 25m/s. what is the ratio of their kinetic energy



so i think i need to use the equation ke=1/2 mv^2
this is how far i got ke=12.5*m and ke=312.5*m
 
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chris.hart said:
it reads, '' two identical objects move with speeds of 5m/s and 25m/s. what is the ratio of their kinetic energy

so i think i need to use the equation ke=1/2 mv^2
this is how far i got ke=12.5*m and ke=312.5*m
Hello chris.hart. Welcome to PF !

What is the ratio of those two numbers?

How does that ratio compare to the ratio of the two speeds?
 
SammyS said:
Hello chris.hart. Welcome to PF !

What is the ratio of those two numbers?

How does that ratio compare to the ratio of the two speeds?


i can't know what the ratio is without finishing the arithmetic? or am i missing something
 
Before using any numbers, write out the ratio using symbols and show us what you get.
 
ratio of their KE somehow means that you need to compare them. How does the first one compare to the second.
 
chris.hart said:
i can't know what the ratio is without finishing the arithmetic? or am i missing something
I get that (312.5m)/(12.5m) = 25.0 .

That's the ratio of the kinetic energy of the faster object to the the kinetic energy of the slower object.
 
thanks guys but i figured out my problem.
id use the formula pe=ke which is the equivalent of mgh * .5mv^2
so i can just simply eliminate the mass on the both sides and solve the equation
 
chris.hart said:
thanks guys but i figured out my problem.
id use the formula pe=ke which is the equivalent of mgh * .5mv^2
so i can just simply eliminate the mass on the both sides and solve the equation

Hmmm potential energy and gravity have nothing to do with this problem.

A ratio of two quantities is just one divided by the other.
 
Last edited:
Since the objects are identical they have the same mass Ek1/Ek2=½mv1^2/½mv2^2=v1^2/v2^2...
 
Last edited:
  • #10
lep11 said:
Since the objects are identical they have the same mass Ek1/Ek2=½mv1/½mv2=v1/v2...
Those velocities should be squared .
 
  • #11
SammyS said:
Those velocities should be squared .
You're right.
 

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