(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Figure 4 shows a partial profile of a roller-coaster ride. Friction and air resistance are negligible. Determine the speed of the coaster at position C if the speed at the top of the highest hill is (a) zero and (b) 5.00m/s

Figure 4 (description)

Point A is the highest point of the rollercoaster. It is 37.8m from the ground. Point B is the lowest point of the rollercoaster. It is 12.8m from the ground. Point C is the mid point of the roller-coaster. It is 17.8m from the ground.

*There are no loops

*From A, it curves downwards to B, then upwards to C

I apologize for not having a picture of this.

2. Relevant equations

E = 0.5mv^2

E = mgh

(sorry, not sure)

3. The attempt at a solution

I have no idea how to start this out...

E = mgh

= m x 9.8m/s^2 x 37.8m *keeping mass as a variable since mass is not given

= 370.44(mass)J

E = 0.5mv^2

370.44(mass)J = 0.5mv^2 *masses cancel out

square root of (370.44J / 0.5) = v

27.22m/s = v

The answer from the textbook: (a) 19.8m/s (b) 20.4m/s

I don't even know how to start out this problem. Help please. Thanks in advance!

EDIT:

for (a) h = 37.8m - 17.8m = 20m

Eg = mgh

= mass x 9.8m/s^2 x 20m

= 196 (mass) J

Ek = 0.5mv^2

196 (mass) J = 0.5mass x v^2 *masses cancel out

Square root: (196J/0.5) = v <- forgot to divide the gravitational potential energy by 0.5

19.8m/s = v

Got the answer for (a) but don't know how to figure out (b)...

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Rollercoaster (finding speed) test tomorrow, please help

**Physics Forums | Science Articles, Homework Help, Discussion**