Question

A 80g particle is moving to the left at 23m/s . How much work must be done on the particle to cause it to move to the right at 45m/s ?

Answer 1

how do i approach the problem

Answer 2

we can see it in this way that we need two works. one to stop the ball and second to give it given velocity.

Answer 3

ok. what i did is to calculate force. of the 80kg , i took 80kg x 9.8. assuming the force of get from here I would use the W=Fxd formula

Answer 4

but hiccup is i don't actually know d because i don't have a time, so I'm thinking i'm probably going to have to use a different equation all together

Answer 5

so what if i going and find KE and then use the Wnet formula that includes delta KE's

Answer 6

you have to use the change in total kinetic energy definition of work.

Answer 7

W= \[DeltaE\]

Answer 8

KE=1/2mv^2 ?

Answer 9

yes, but the change in this energy will give Work. here you can forget about the potential energy difference cause the body is moving horizontally.

Answer 10

ok. i think i'm understanding it. so use KE formula from above for both, then take deltaE of the KE and that should provide my answer?

Answer 11

not directly the answer but a part of it then you can do it again to provide it the given velocity then add 'em up to get your full answer. not that hard really

Answer 12

i now think i'm lost with your explanation. sorry, i just don't understand the energy/work things

Answer 13

work= change in total energy
W= E2-E1

Answer 14

yea i understand that

Answer 15

i get 59840, can you clarify for me is E and KE synonymous in this problem?

Answer 16

from here you get W1.

as long as we don't mess with PE, yes, we get KE for E