Question

A roller coaster has a mass of 275 kg. It sits at the top of a hill with height 85 m. If it drops from this hill, how fast is it going when it reaches the bottom? (Assume there is no air resistance or friction.)

A. 18.0 m/s
B. 29.9 m/s
C. 73.4 m/s
D. 40.8 m/s

Just need to know how to work problems that are similar.

Answer 1

when the roller coaster is on top of the hill, it has GRAVITATIONAL POTENTIAL ENERGY.
bt when it reaches the bottom that GPE coverts to KINETIC ENERGY

Answer 2

so u have to find the GPE and wht ever is your answer..that would also equal to KE
PE=KE

Answer 3

EP= mgh

Answer 4

so, its 275*9.8*85

Answer 5

WEll you can here conserve the total mechanicl energy
so at the top,total mech. E=mgh
and at the bottom its =1/2m[v ^{2}]
also you can use newton's third law i.e 2gh=(v-u)(v+u),,where initial vel u=0 at the top and
v=final vel. at bottom

Answer 6

now just calculate the answer

Answer 7

Thanks so much(: I don't understand physics and I just need to finish this class online to graduate in 2 weeks.

Answer 8

@RANE i think the ans is(2*9.8* 85)^1/2

Answer 9

PE= mgh

Answer 10

where did u get 1/2 from?

Answer 11

well 1/2mv^2=mgh

Answer 12

yes bt right now u r looking for PE

Answer 13

when the roller coater will move down it will transfer its PE to KE because its no more above the ground level

Answer 14

With the (1/2) it comes to 833. That isn't right

Answer 15

exactly, u have to use PE @DaniRae231

Answer 16

well its not half its under root..
ans is 41.smthng

Answer 17

40.8 m/s

Answer 18

whts the answer given to u ? @DaniRae231

Answer 19

Its an online class. I answer it and it tells me if I got it right or not. It's APEX.

Answer 20

@DaniRae231 yes i too got that

Answer 21

u can not use EK formula when u r supposed to find PE becoz its above the ground level...and also its not moving

Answer 22

if an object is not moving then how can u use kinetic energy

Answer 23

well we have to find the final velocity....so we conserve the mech. energy
at the top its only mgh( vel =0)
and at the bottom its 1/2mv^2(h =0)....so mgh =1/2mv^2

Answer 24

@RANE ,i didnt get u

Answer 25

ok... when do u calculate PE

Answer 26

i mean when its moving or its above the ground level

Answer 27

well potential energy ,when it is above the ground

Answer 28

exactly, now do u know that energy is never lost right?

Answer 29

perfectly

Answer 30

wait wht grade r u in?

Answer 31

m in 12th stndrd..why?

Answer 32

no, just asking..anyway
if roller coaster is above the ground at rest it has PE bt as it starts to come doen that PE starts to covert in to kinetic energy

Answer 33

yes or we can say pot energy decreases and kinetic energy starts to increase...

Answer 34

yes

Answer 35

Well I already have it, so it doesn't matter to me...

Answer 36

and in which grade u are @RANE ?

Answer 37

so since there is no lost in energy then PE= KE
if u calculate the potential energy (since it's mgh and m and h is given to u) it will equal to kinetic enrgy at the bottom

Answer 38

yes i also did the same..you are very correct

Answer 39

umm. so it means that u understood y we cant use 1/2 in calculation

Answer 40

Alright, this is just a Junior science Physics class. I just failed it my junior year, so they have me doing it online.

Answer 41

this is just the basic of energy conservation in phys...

Answer 42

no...i jus actually said that potential energy at the top(mgh)=kinetic energy at the bottom(1/2m(v)^2)...so 1/2 will come for sure

Answer 43

no!!!

Answer 44

omg

Answer 45

why..i want to know!

Answer 46

now i will just recommend u to use google or ask your teacher

Answer 47

well tell me coz i think m correct

Answer 48

LOL no u r not correct

Answer 49

just go nd study conservation of energy

Answer 50

see at the top total mech energy=mgh + 1/2m(0)^2
=mgh + 0

nw at the bottom total mech energy=mg(0) +1/2mv^2
hence they will b conserved...sry i think u got it totally wrong
@RANE..n the ans is also there

Answer 51

noooooo........
i've dont these for one hole term this yr which is only 4 wks ago when i did my final examination on it
so u can not tell me that i got my answers rong in my exam and top of that the exam markers also marked them wrong

Answer 52

only one way to sort it out...how did u do it?