2.2.6_phys.docx.pdf

Document Content and Description Below

Question 1 (8 points) You are going 30 m/s in a car of mass 1000 kg when you reach a red light and stop your car. a. How much heat energy is released by the brakes of your car? (1 point) KE = ½mv�... � = 450000 J b. If your car could recapture 40% of the heat energy released from your brakes, how much energy would you recapture? (1 point) You'd recapture 180000 J c. Imagine that you have an electric car and all of the recaptured energy is put back into the battery that powers your car. What speed could your car achieve from rest by using only the recaptured energy from part (b)? (2 points) 180000 J = ½ * 1000kg * v² v = 19 m/s d. If you brake from the speed in part (c) and then start again from rest, how fast will you be able to drive? (2 points) 26.6 m/s An advertisement says that if you have regenerative brakes like these, you'll never have to put any more energy into your car again. Is this true or false? Explain your answer. (2 points) False because if you’re on the highway and don’t break for a very long time you will need energy. While you may need it less, you will still need it. Question 2 (4 points) Andrea rides her bicycle at a speed of 10 m/s. She and the bike have a combined mass of 50 kg. a. If she uses her brakes to slow down to 5 m/s, how much energy is converted to heat? (1 point) Heat energy = ½ * 50 * 10^2 – ½ * 50 * 5^2 = 1875 J [Show More]

Last updated: 1 year ago

Preview 1 out of 5 pages