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Reading Quiz

Reading Quiz. Which of the following statements is FALSE Speed, velocity, and acceleration are each defined as vectors "A car moving in a circle at a constant speed of 30 mph is accelerating "The instantaneous speed of a moving car can be different from its average speed. Newtonian Revolution.

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Reading Quiz

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  1. Reading Quiz Which of the following statements is FALSE • Speed, velocity, and acceleration are each defined as vectors • "A car moving in a circle at a constant speed of 30 mph is accelerating • "The instantaneous speed of a moving car can be different from its average speed PHYS 214: The Nature of Physics

  2. Newtonian Revolution The Force equals the Motion ( F = ma ) Newton’s Laws An object remains at rest, or in uniform motion in a straight line, unless it is compelled to change by an externally imposed force. The acceleration of an object is directly proportional to the magnitude of the imposed force and inversely proportional to the mass of the object. For every action there is an equal and opposite reaction. PHYS 214: The Nature of Physics

  3. Academic Integrity • Never give your HIP password to anybody else. • All CHIP Reading Quiz and HW answers must be your own. • Consulting with others on HW is fine, as long as you are not just being given the answers. • When permitted, Lecture Quiz answers may follow consultation with others. • Any cheating on exams will earn an F in the class, and formal disciplinary proceedings. PHYS 214: The Nature of Physics

  4. Classroom Demeanor • Come to lectures to listen and participate. • No personal conversations with friends during lecture! • Don’t get up to leave before 8:20 AM if lecture has not ended. • Join in on the Lecture Quiz discussions. • Interrupt if you have a question. PHYS 214: The Nature of Physics

  5. SPEED Speed equals distance covered divided by the time needed to move that distance : S=d/t. Average speed refers to a large time interval: If it takes three hours for a race car to complete the Indianapolis 500 race, its average speed was s=500 miles / 3 hours = 166.7 mph. Its fastest speed was probably more than 200 mph. Its slowest speed was exactly 0 mph, when the engine was started. These are examples of instantaneous speeds. These correspond to speeds over very short time intervals. PHYS 214: The Nature of Physics

  6. Instantaneous Speed S=Dd/Dt. A very small time PHYS 214: The Nature of Physics

  7. Velocity Velocity describes the speed of an object and the direction it travels. Such a quantity is called a vector. Direction can be described as North, South, etc., or it can be described mathematically, e.g. along the x-axis, the y-axis, etc. Vectors are often drawn as arrows. A larger velocity would be given a longer arrow. PHYS 214: The Nature of Physics

  8. Question 5: Consider various types of weather maps and navigational maps of the North Atlantic, that plot out temperatures, storm conditions, etc. Which of the following quantities might best be represented as vectors on the map? Air temperature Water temperature Ocean currents Barometric pressure None of the above PHYS 214: The Nature of Physics

  9. Figure 2.5The direction of the velocity changes as the car moves around the curve, so that the velocity v2 is not the same as the velocity v1 even though the speed has not changed. PHYS 214: The Nature of Physics

  10. Figure 2.6The direction of the velocity changes whena ball bounces from a wall. The wall exerts a force on the ball in order to produce this change. PHYS 214: The Nature of Physics

  11. Acceleration Acceleration is the change in the velocity of an object during a certain time interval. [If a car is moving in the positive direction] A car that speeds up has a positive acceleration. A car that slows down has a negative acceleration. Acceleration = {final velocity - initial velocity}/time Because Acceleration is a vector; a negative acceleration can mean that the car is speeding up in the negative direction! PHYS 214: The Nature of Physics

  12. Summary of Chapter 2: Speed is distance divided by time. “Average” speed is over a longer time interval; “instantaneous” is over the shortest possible time. Velocity is a vector which denotes both the size of the speed, as well as its direction. Acceleration is how much the velocity changes during a specified time interval: PHYS 214: The Nature of Physics

  13. Question 5: Consider what happens when the far end of the track is lifted up. The ball will move up, then roll back down. Which of these is true: First the acceleration is positive, then it is negative. The acceleration is constant. The velocity is constant. The speed is constant, but the velocity changes. None of the above. PHYS 214: The Nature of Physics

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