Can someone check if my answer are right please ! Im not 100% sure about them. 1
ID: 1591873 • Letter: C
Question
Can someone check if my answer are right please ! Im not 100% sure about them.
1. Your are standing with your 1,250-kg car at a red light. The light turns green, and you speed up your car to 47 mph. What is the total work done on your car?
275,861.3J
2.Your are standing with your 1,212-kg car at a red light. The light turns green, and you speed up your car to 59 mph. Then you continue at a constant speed. After another mile, what is the total work done on your car from the moment you started from rest?
421,494.2J
3.Your are driving your 1,185-kg car at a speed of 30 mph. A traffic light in front of you turns red and you bring your car to a complete stop. What is the total work done on your car?
-106,548.1J
Explanation / Answer
Question 1 is correct:
W = 1/2 mV2
V = 47 * 1609/3600 = 21 m/s
W = 0.5 * 1250 * 212 = 275,792.73 J
Question 2 is also correct
W =Kf -Ki = mv2/2 - mu2/2
But u = 0 so:
W = 1/2 mV2 V = 59 * 1609/3600 = 26.37 m/s
W = 0.5*1212*26.372 = 421,398.40 J
Question 3 is correct too.
W = Kf - Ki = 0 - Ki
V = 30 * 1609/3600 = 13.41 m/s
W = 0.5*1185*13.412 = -106,548.15 J
You don't need to get worried about your results and mine, there's a little difference between them and only in the decimals.
Hope this helps