TOC: VE examples, VE student surveys, VE diagnostic questions Virtual Experiments Examples

Size: px

Start display at page:

Download "TOC: VE examples, VE student surveys, VE diagnostic questions Virtual Experiments Examples"

Basil Norris
5 years ago
Views:

TOC: VE examples, VE student surveys, VE diagnostic questions Virtual Experiments Examples Circular Motion In this activity, students are asked to exert a force on an object, which has an initial

1 TOC: VE examples, VE student surveys, VE diagnostic questions Virtual Experiments Examples Circular Motion In this activity, students are asked to exert a force on an object, which has an initial velocity, so that it can move in a uniform circle indicated by a white dashed line. The frictional force is usually set to be zero in the beginning. Figure 1 shows the screen shot of the VE. This activity allows students to explore their ideas about circular motion. Usually, students would predict that they should exert a force along the circle (or with a small angle) as if they were dragging the object similar to what they would do in real world. As students start to play and test their predictions, they quickly discover that their predicted method won t work. After a few try and error, most students can arrive at the conclusion that the force has to have a constant magnitude but with a constantly changing direction always pointing towards the center of the circle. We have tested this program with high school students and college students. It often takes them about 10 minutes to figure out how to exert the force. After the first phase, the instructor can remind students to turn on the friction and explore how their answers would be different. With proper guidance, this further exploration can often help students achieve a deeper level understanding of forces involved in circular motions. Collision Figure 1. Screen shot of the circular motion VE program. This is a program that we just finished and is to be tested in the autumn quarter of The primary motivation to develop this VE is to show the fine details occurred during a collision, which are often difficult to explain with current instructional tools. The scenery is very similar to the linear motion activity except that we now have two carts that are each mounted with a bumper (Figure 2). During the

2 collision, the bumpers will deform according to the forces interacting between the two carts. There are many modifiable variables including the mass and initial velocity of each cart, the friction of the road, the hardiness of each of the bumper, and the external forces during the collision that can be applied interactively in real-time. In real world, most collisions happen very quickly, which make it very difficult for students to observe details of the process such as the deformation of the objects. In this VE, once the collision starts, we put the simulation is slow motion that can be adjusted from real-time to 100 times slower. In addition, the velocities, positions, and forces on the two carts are also shown in real-time both in diagrams and in numerically labeled vectors which also change their lengths accordingly. With the many different representations integrated in a single activity, the flexibility of easily changing different variables, and the slow motion for showing the details of the collision process, students can conveniently test their hypothesis and explore possible alternatives in a very time-efficient manner. For example, students often believe that during a collision a hard object may exert a larger force than a soft object would exert. This is very hard to test with a real experiment, especially if we want to show what features are different and what keep the same when hard meets soft. Using this VE, one can modify the hardiness of the two bumpers and let it go to observe the phenomenon. The results will clearly show equal and opposite interacting forces but different deformations of the bumpers. In this way, students can more comfortably accept the results, since they always believed that there must be something different when hard meets soft. But in traditional instruction, the teachers had no good tool to explain what really is different and can only tell the students that the interacting forces have to have the same magnitude and opposite directions. Students may be able to memorize this, but intuitively many would consider it a magic. Figure 2. Screen shot of the collision VE program.

3 131 Lab quiz Week 8 1. Please compare the virtual reality labs (using the new computers and joysticks) to the regular labs: a. Which did you find more helpful or relevant in the context of the course? b. Which more effectively addressed the physics concepts it was intended to address? c. Which did you learn more from? d. Which were more enjoyable? 2. From the answers you gave to question 1, please pick at least one item you feel strongly about and explain your answer in detail. What did you prefer and why? 3. Interacting with simulated objects using the joystick gives you a chance to directly experience the way force effects motion. Did this help you understand forces or was it not any more helpful than the standard lab equipment? 4. Comment on the difficulty of the new virtual reality labs. Where they too easy or hard, were the directions clear or unclear? (Also, please indicate which new lab you did week 3 or week 8.) 5. What physics topics would you like to address using a virtual reality environment? 6. Of all the labs you did in 131, which one did you like best and why? Which one did you least enjoy and why? 7. What change(s) would you suggest to make lab a more useful part of the overall physics course?

4 ADDITIONAL DIAGNOSTIC TEST QUESTIONS: INSTRUCTIONS: When you are done with the FCI Diagnostic test questions, answer these questions on the same bubble sheet. The FCI has 30 questions, so make sure you start bubbling the answers for these additional questions at number 31 on your bubble sheet. 31. You're riding in a friend's car (wearing your seat belt, of course) when suddenly they slam on the brakes to avoid hitting a cat. What do you feel while the car is screeching to a halt? (If you feel that more than one of these forces is present, bubble in all answers that apply.) (A) Your seat applies a force on you towards the front of the car. (B) Your seat applies a force on you towards the front of the car, but that force grows weaker. (C) Your seat belt applies a force on you towards the back of the car. (D) Nothing no forces are applied to you during the breaking. 32. You are coasting along at a constant speed on a skateboard. What forces are you feeling? (A) Just the wind. (B) The skateboard applies a constant forward force on your feet. (C) The skateboard applies a constant backward force on your feet. (D) You don t feel any forces; however, you are carrying with you the force of your motion. 33. You are fouled while playing basketball and have the chance to impress your friends with your shooting skills. Your free throw is perfect, the ball goes through the basket without touching the rim. After the ball leaves your hands, at what point are the forces on the ball the strongest? (A) Right after it leaves your hands. (B) At the highest point of its arc before coming back down. (C) Right before it hits the ground. (D) None of the above; the forces are the same at every point.

5 34. You've just gotten out of class late and are running down the stairs to get to your next class. You reach a landing and need to turn around quickly so you instinctively grab the end of the railing with your inside arm. How would you explain this in terms of physics? (If you feel that more than one of these answers gives a correct physical reason, bubble in all of them you think are right.) (A) This allows you to pull to apply a force on your body towards the railing which causes you to move around the railing's end in a semicircle and without slowing down. (B) Holding on to the railing keeps you from falling over as you make a very quick turn, but doesn't help you make the turn itself. (C) Since your arm prevents you from continuing forwards, you naturally swing around to face the other direction and can keep going down. (D) With the railing for leverage, you can pull yourself around the corner. 35. Suppose a bowling ball is originally moving in a straight line with a constant speed. There is some friction between the bowling ball and the floor. You have a hammer in your hand and can hit the ball many times. In what direction should you hit the ball so that it will move in a circle at its original speed? (A) A little towards the outside of the circle. (B) Same as the motion, tangent to the circle. (C) A little towards the inside of the circle. (D) Right towards the center of the circle. C D B A 36. Feeling nostalgic, you and your friends are hanging out in a playground. You decide to ride on the merry-go-round without holding on, just sitting near the edge. A friend gives it a good shove, and now you are moving around a circle at constant speed. What forces do you feel? (If you agree with more than one of the choices, pick as many of them as you feel are relevant.) (A) A force pulling/pushing you to the outside. (B) A force pulling/pushing you along the tangent line. (C) A force holding you in place. (D) You don't feel any force; you just move with the object.

6 37. You are a tennis ball. You are hit by a racket. Which statement is true? (A) You feel a force from the racket which is stronger than the force you exert back on the racket. (B) You feel a force from the racket which is weaker than the force you exert back on the racket. (C) You feel a force from the racket which is the same in strength as the force you exert back on the racket. (D) You and the racket both exert forces on each other, but their strengths depend on which object was originally moving faster. 38. As in the previous question, you are a tennis ball but now you are being thrown horizontally against a wall. Which statement is true? (A) You feel a force from the wall which is stronger than the force you exert back on the wall. (B) You feel a force from the wall which is weaker than the force you exert back on the wall. (C) You feel a force from the wall which is the same in strength as the force you exert back on the wall. (D) You exert a force on the wall, but being just a wall, it does not exert a force back on you. 39. You and your friends have noticed a can floating in a lake near the shore. You decide to have a competition to move the can the furthest by throwing something at it. You each have a piece of silly putty and a hard rubber ball (the ball and putty are the same size and have the same mass). Which object should you choose, and why? (If you feel that more than one of these answers gives a correct physical reason, bubble in all of them you think are right.) (A) The hard rubber ball because it will bounce back, which means you can give the can more speed. (B) The hard rubber ball because a hard object will always provide more force than a soft object in a collision. (C) The silly putty because when it sticks it will carry the can along with it. (D) The silly putty because when it sticks it will transfer its energy to the can, giving it the speed you need to win.

Disciplinary Core Ideas

Disciplinary Core Ideas Addresses NGSS Level of Difficulty: 1 Grade Range: K-2 OVERVIEW In this activity, students will compare two forces of energy on the motion, velocity, and direction of an object. Students will examine how