PHYS 1403 Lab Homework Work and Energ This homework will be due when you come to
ID: 1790585 • Letter: P
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PHYS 1403 Lab Homework Work and Energ This homework will be due when you come to lab the week of October 30. All of these exercises should be done by using the concepts of work and enery. NOT kinematics 1) In screeching to a halt, a car leaves skid marks that are 65m long. The coefficient of kinetic friction between the tires and the road is -0.71. How fast was the car going before the driver applied the brakes? Show your work and explain your reasoning 2) Consider the diagram below 30m a) The roller coaster is pulled up to point A where it, and its screaming occupants, are released from rest. Assuming no friction, calculate the speed of the coaster at points B, C. and D. Show your work. b) Now, suppose the roller coaster passes point A with a speed of 1.70m/s. If the work done by friction is 45,000J, with what speed will it reach B? The mass of the coaster is 1000kg. Show your work 3) A 500 kg hot air balloon begins at rest and rises. The wind and lift forces combined do 97,000 J of work on the balloon. At what height above the surface of Earth is the speed of the balloon 8.00m/s.Explanation / Answer
3 )
using energy conservation
initially there is no energy , work done by wind and lift is external force
0 = mv^2/2 + mgh - 97000
m = 500 kg
v = 8 m/s
0 = 16000 + 4900h - 97000
h = 16.53 m
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