Question

MEDAL!!!!


If i'm driving in a car at 30kph and a friend is driving in a car with the same mass at 60kph, my friend's car's kinetic energy is bigger than mine by a factor of what? (that is, divide my friend's over mine.)

Answer 1

@jim_thompson5910

Answer 2

Hint:

Kinetic Energy (KE)

KE = (1/2)*m*v^2


m = mass
v = velocity

Answer 3

well since it said that the masses are the same, it would eventually cancel out. however, the velocity would be different because one is going 60 kph and the other is going 30 kph.

thus, would i do:
\[\frac{ 60^2 }{ 30^2 } = \frac{ 3600 }{ 900 } = 4 ? \]

Answer 4

correct, the friend has 4 times more KE

Answer 5

i just wanted to make sure what the units would be.

Answer 6

would it just be J , like 4J

Answer 7

The joule units would cancel though

Answer 8

only 4 right?

Answer 9

example:

your car
m = 100
v = 30

friends car
m = 100
v = 60

-------------------------------------------------------

Your KE

KE = (1/2)*m*v^2
KE = (1/2)*100*30^2
K = 45,000


Friends KE

KE = (1/2)*m*v^2
KE = (1/2)*100*60^2
K = 180,000


Ratio of the two KE values
180,000/45,000 = 4

whatever the units for the KE were, they cancel out when you divide

Answer 10

yeah only 4

Answer 11

okay thanks :)

Answer 12

np

Answer 13

so there is also another question on the difference on potential and kinetic energy

Answer 14

@jim_thompson5910

Answer 15

i wrote: "potential energy is the amount of energy in an object when it is still and at a certain position, however, kinetic energy is when you're calculating the amount of energy of an object when it is moving."

Answer 16

will that be fine?

Answer 17

potential energy (PE) is the amount of stored energy that can be used and converted into KE

example: pick up a rock and place it on a ledge. It has PE stored up. When you push it off the ledge, it speeds up and hits the ground converting that PE into KE

Answer 18

potential energy due to gravity

PE = m*g*h