Exploration Series. BOBSLED Interactive Physics Simulation Page 01

Transcription

1 BOBSLED Interactive Physics Simulation Page 01

2 What keeps the bobsled on the track? The bobsled gains speed as it flies down the nearly frictionless track.the riders must take the turns just right to maximize their performance. When turning, the contact force between the track and the runners underneath provides the centripetal force. When the bobsled is traveling more quickly, more force is required to turn it. To access this physics simulation visit: Page 02

3 Speed - The higher the speed of the bobsled, the greater acceleration is required to change its direction in a turn. This means more force is required if the bobsled is really moving quickly. Turn Radius - When the turn is very tight, the velocity is changing quickly - not in magnitude (speed) necessarily, but in direction! Tighter turns require higher net (unbalanced) forces because the velocity is changing rapidly in direction - and this means the bobsled is accelerating quickly. Mass - Increasing the mass of the bobsled impacts the simulation in two different ways. First, it means the gravitational force (weight) acting on the bobsled is higher, and so the normal force will adjust as well. Second, it means that the bobsled has more inertia, and greater force is required to turn it away from a straight line. Force Diagram - Assuming friction is low (which is why we are on sleds on ice), there are only two important forces acting on the bobsled: gravity (weight) and the contact (normal) force acting between the sled and the track. To access this physics simulation visit: Page 03

4 Centripetal Force Vs. Speed - Greater speeds mean greater velocity, and therefore greater force required to change the direction of velocity as the bobsled turns. This graph represents that relationship. Centripetal Force Vs. Turn Radius - Turns with greater radius require less rapid changes in the direction of the bobsled, and so require less force to execute. This graph represents that relationship. To access this physics simulation visit: Page 04

5 A 200 kg bobsled is traveling at 15 m/s around a turn with radius 10 m. For what turn radius would the centripetal force required be exactly half as high? (Set the mass slider to 200 kg and the speed to 15 m/s. Find a turn radius that drops the centripetal force by half.) Let's say the turn is 20 m in radius. For what mass and speed is the horizontal component of the normal force equal to 4000 N? (Adjust the sliders so that the horizontal component of the normal force is equal to 4000 N. Set the turn radius to 20 m.) When is the centripetal force acting on the bobsled highest? (Adjust the sliders so that the centripetal force acting on the bobsled is as high as possible.) To access this physics simulation visit: Page 05

6 Challenge ME! What is the relationship between speed and the centripetal force required to turn the bobsled? What is the relationship between the radius of the turn and the centripetal force required to turn? What is the relationship between the mass of the bobsled and the centripetal force required to turn? If a bobsled is moving at constant speed, but turning, is it accelerating? Is there an unbalanced force acting on it? Need Help? Check out the Bobsled Walkthrough video at: To access this physics simulation visit: Page 06

7 Why are freeways banked? On a flat roadway, the force of friction is critical to a car making a turn and not sliding off of the road. You can imagine that, when conditions are bad - like on a rainy day - there isn't as much friction force available to allow fast-moving cars to make the turn. By banking the turn, you allow some of the normal (contact) force between the car and the road to assist in making the turn. This contact force won't vary with weather conditions. How does the marble stay in the glass? When the marble is moving around & around in a circle, the normal (contact) force between the marble and the glass walls pushes inward. Now that the marble and glass are in good, firm contact, a frictional force can arise that prevents the marble from moving downward. The shape of the glass can help with this too: if there's a component of the normal force upward, the marble has even more support against gravity. Is our Sun accelerating? Yes, in many different ways. First, the Sun accelerates in response to the force of gravity acting on it from all the different planets and other bodies in our solar system. (We use this effect, in fact, to find planets around other stars!) Second, the Sun is just one star in the Milky Way Galaxy. The whole galaxy is rotating, and so all of the stars within it feel centripetal forces. Astronomers believe that the force keeping the galaxy from flying apart is the gravitation of some unseen dark matter that fills the galaxy. How fast would the Earth have to spin for us to 'fly off'? The Earth's gravity is more than enough to keep us from flying off, even at the equator. Still, the fact is that we are moving in a circle around the belly of the Earth as it rotates means that there needs to be a greater inward than outward force. This amounts to a roughly 0.3% difference between the normal force acting on us and our gravitational weight at the equator. If the Earth spun so quickly that the normal force disappeared, the day would be less than an hour and a half long! To access this physics simulation visit: Page 07

8 Physics Concepts Click on the link below to learn more. Centripetal Force Problems - To access this physics simulation visit: Page 08