﻿ Twister at Gröna Lund

## TWISTER

Gröna Lund's new roller coaster, Twister, winds in and out through Kvasten, Jetline and Vilda Musen, next to the water, giving strong visual impressions adding to the intensity of the ride. But what is the physics behind the experience of the body?

### Facts

• Train length: 7.3 m
• Lift hill: height 15.4 m.
• Maximum slope in the first drop: 56o
• Height of first drop: 14.7m
• Radius of curvature at the bottom of the first valley: 14.3 m
• Height of next hill: 8.6 m
... with a radius of curvature at the top: 10.7 m.

### Exercises

The Lift Hill
• What forces act on a person moving up the lift hill with constant speed?

#### The first drop

• Draw the forces acting on a person on the way down in the first drop!
• How large is the acceleration on the way down?
• What force does the train excert on the rider?

#### The first valley

• What is the speed of the train during the first valley? (Neglect energy losses and train length)
• Draw a diagram showing the forces on the rider in the bottom of the valley!
• Use the energy principle to estimate the normal force at the bottom on a person with mass M.
• Does it matter which if you choose a seat in the front, middle or back of the train? Explain!

#### Next hill

• How fast do you expect the train to move across the highest point?
• What forces act on the rider?
• Additional problem How large is the difference in normal force at the top, depending on your position in the train?

#### Twister Coordinates

You can study the Twister track in more detail by describing e.g. the first hill in Twister coordinates, that can be converted to normal coordinates by using the distance 1.4m between the vertical beams and 1.8 m between the horizontal beams. (Needs photo)

#### Measurements at Gröna Lund

On site, use e.g. your mobile phone stopwatch to measure the time required for a train to pass the lowest (or highest) points. Since you know the length of a train, you can work out the speed. How does it compare to the theoretical calculations? What can lead to discrepancies?
http://physics.gu.se/LISEBERG/gl/TWISTER/twister_eng.html
Ann-Marie.Pendrill@fysik.lu.se
, Feb 2011