Mean em 5.00 wcD Physics 235 Exam#1 NAME: 17. A green 30 kg wagon is moving west
ID: 1583809 • Letter: M
Question
Mean em 5.00 wcD Physics 235 Exam#1 NAME: 17. A green 30 kg wagon is moving westward at 4.0 m/s. What is the value of the KE of the green brick? a) 450 J b) 240J c) 300 J d) 480J e) 1,800 J 18. How much work is needed to stop the green brick? a) 450 J b) 240 J c) 300 J d) 480J e) 1,8001 19. Suppose that the green brick is stopped in a distance of 8.0 m. What is the average net force on it? a) 30N b) 60 N c) 80N d) 225 N e) Not enough info. 20. If this net forceis supplied by friction, what is the coefficient of kinetic friction between the green brick and the surface? a) 0.2 b)20 c) 10 d) 1.0 e) 0.1 4 of 4Explanation / Answer
17) kinetic energy=(1/2)m v^2=(1/2)*30*(4)^2=240 J
18) Work done is change in kinetic energy
Work needed =Kinetic energy=240J
19)W=F.d
F=W/d=240/8=30 N
20)f=mu* N=mu * mg
30=mu* 30*10
mu=0.1