Question

Please help with a few questions?
A 175 kg motorcycle has 6.8 x 104J of kinetic energy. How fast is it going?

Answer 1

@TheSmartOne @Here_to_Help15

Answer 2

what is the formula that defines kinetic energy?

Answer 3

Thats all I need the formula

Answer 4

the question assumes that you have been taught the formula, and is asking you to apply it.

Answer 5

yes

Answer 6

what is your best recollection of the formula?

Answer 7

I can not find it in my formula notes... I have all of them but this one...

Answer 8

This one and one other

Answer 9

well, im of the mindset that it would be easier for you to remember/learn if you can find it and post it. try a google search for kinetic energy formula and it should pop up pretty easily. afterwards i can confirm it or correct it if need be.

Answer 10

even a vague recollection would be useful :)

Answer 11

k=1/2mv^2

Answer 12

I have this one in my notes

Answer 13

very good and all we need to do is solve for v

Answer 14

175=1/26.8*10^2

Answer 15

175 kg motorcycle has 6.8 x 104J of kinetic energ

\[6.8(10^4)=\frac{175}{2}v^2\]
one stray thought, is 175 mass or weight? im assuming its the mass.
\[\frac{2}{175}(6.8)(10^4)=v^2\]
\[\sqrt{\frac{2}{175}(6.8)(10^4)}=v\]

Answer 16

so would 10 become 10000?

Answer 17

sqrt(10^4) = 10^2 = 100

Answer 18

okay

Answer 19

So it would be 28 m/s

Answer 20

http://www.wolframalpha.com/input/?i=sqrt%282%286.8%29%2810%5E4%29%2F175%29

yes, that is what im coming up with as well

Answer 21

okay I have one more question can you please help me with?

Answer 22

i can try

Answer 23

A force of 35 N is used to stretch a spring 15 cm beyond its normal length. What is the increase in the spring’s energy?

Answer 24

I dont know why there are question marks....

Answer 25

its an encoding issue on the site. a refresh clears them up

Answer 26

tends to happen alot for copy/paste stuff

Answer 27

okay so all my formulas involving this equation need m but I have cm?

Answer 28

convert if need be

1m = 100cm; therefore 1cm = 1/100 m

15cm = 15/100 m = .15m

Answer 29

okay thank you for that!

Answer 30

youre welcome

i had to look up an energy equation for this:

\[PE=\frac12kx^2\]
and using the k from the spring constant:\[F=kx~:~k=F/x\]
\[PE=\frac12 Fx\]

Answer 31

does that seem right to you?

Answer 32

U=mgh

Answer 33

I dont know how to fill the numbers in?

Answer 34

Thats what I found...

Answer 35

lets use the Fx/2 :)

http://www.physicsclassroom.com/Class/energy/u5l1b.cfm

Answer 36

PE = 35(.15)/2

PE = 35(.075)

Answer 37

sorry I lost connection @amistre64

Answer 38

site was on the fritz for me as well.

Answer 39

I got an extreamly weird answer .07

Answer 40

i get about 2.6 :)

Answer 41

from the site i looked at:

PE = 1/2 kx^2, given that: F = kx

since we have F and x, we can rewrite this as:

PE = 1/2 Fx^2/2 or simply:

PE = Fx/2

Answer 42

That makes much more sence!

Answer 43

good luck