I need help with 2 questions, please! Q1.) A 3230 kg bus is traveling 21.0 m/s t
ID: 1782395 • Letter: I
Question
I need help with 2 questions, please!
Q1.) A 3230 kg bus is traveling 21.0 m/s towards a bridge when the bus driver notices that the bridge is under construction. If the bus driver slams on the brakes and the tires skid to a stop, what is the change in thermal energy of the bus and the road surface?
Options: (3.56×105 J) (2.85×106 J) (844 J) (7.12×105 J)
Q2.) A rope is used to lift a 26.5 kg sheet of shingles to roofers 4.70 m on top of a house. Using work and energy, solve for the tension in the rope if the speed of the shingles is 2.35 m/s when they reach the roof.
Options: (275 N) (6.08×103 N) (1.29×103 N) (244 N)
Explanation / Answer
asumming all KE is converted into TE
THERMAL ENERGY=1/2*3230*(21.0)^2
=7.12*10^5J
option D.
GPE=mgh=26.5(9.81)(4.70)
=1221J
V=2.35m/s
Vavg=2.35/2=1.17m/s
time to lift shingles=t=h/Vavg
=4.70/1.17=4.0170s.
acceleration of lift=2.35/4.0170s
=0.585m/s^2
tension in rope=m(g+0.585)
=26.5(9.81+0.585m/s)
=275N.
OPTION:A.
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