Projects: UDL : UDL Friction Activity 5-6 Penny heat
This page last changed on Oct 15, 2007 by ehazzard.
scaffolding needs editing
Does friction create heat?
Cannot resolve external resource into attachment.
1. Rub your hands together, first slowly and then quickly. You probably notice that your skin warms up when you rub your hands quickly. Why do you think this happens? ANSWER BOX
2. Hold a penny against your cheek to feel its temperature. Rub the penny on a hard surface, like a block of wood. Don't use a surface that could be damaged. Rub it in a circle twenty times. Then test the temperature of the penny again by holding it against your cheek.
You probably noticed that the penny heats up. If there were no friction, would the penny heat up? ANSWER BOX
3. Is it your finger that makes it hot, or the rubbing?
4. Which of these things would make the penny heat up? You could choose more than one. (multiple selection question)
1. Now let's test your choices to the above questions using a surface temperature sensor. Cut out a 2 x 4 cm piece of cardboard.
2. Coat one side of the cardboard and one side of 4 pennies with rubber cement.
3. Make a sandwich with the sensor between the penny and the cardboard. The sides coated with rubber cement should face each other (inside the sandwich). The rubber cement will provide friction between the penny and the cardboard.
4. Put the penny on a block of wood. Hold the cardboard by the edges so that your fingers don't affect the temperature of the penny.
5. Start the sensor. Note the temperature of the penny before you start touching, rubbing or pushing the penny.
6. Hold the penny down by pressing on the edges of the cardboard. Have one student rub with the penny and another student count out seconds. Rub the penny slowly for 10 seconds, then stop for 5 seconds, and then faster for 10 seconds on the wood block. Try to push down with the same amount of force! Look at the graph.
7. Describe the graph. Which had more heating effect, rubbing slowly or rubbing fast? ANSWER BOX
8. Move the sensor and cardboard to another penny and make a new sandwich. Start the sensor and note the starting temperature of the penny.
9. Push down lightly with the cardboard and rub the penny for 10 seconds, then stop for 5 seconds, then push down hard and rub it for 10 seconds, then stop. Look at the graph.
10. Which had more heating effect, pushing down lightly or pushing down hard? ANSWER BOX
Heat is a form of energy, so it takes energy to heat up a penny.
Explain why the heating effect of rubbing fast would be different from the heating effect of rubbing slowly.
Explain why the heating effect of pushing hard would be different from the heating effect of pushing lightly.
1. Move the sensor and cardboard to another penny and make a new sandwich. Place a sheet of waxed paper on a part of the wood. Start the sensor and note the starting temperature of the penny.
2. Rub the penny for 10 seconds on the wood, then move it to the waxed paper and rub it for 10 seconds on the waxed paper, then stop. Look at the graph.
3. Describe the graph. Which caused more heating, rubbing on the wood or rubbing on the waxed paper?
Automobile brakes heat up a lot when a car comes to a stop. The heat energy comes from the energy of motion of the car. Based on your experiments with a penny, answer these questions.
Explain your answer.
Which would cause more heating in the brakes?
Explain your answer.
|Document generated by Confluence on Jan 27, 2014 16:49|