A 4 kg block with a 1 kg block stacked on top initially slides at 2 m/s on a rough, horizontal
surface. The blocks continue to move as a unit with no sliding between the two. The blocks come to rest 1 m
away.

15. How much work did kinetic friction from the surface below do on the 4 kg block during this process?
a) -2 J
b) -6 J
c) -10 J
d) -14 J
e) -18 J

16. How much work did static friction from the 1 kg block above do on the 4 kg block during this process?
a) +2 J
b) +6 J
c) +10 J
d) +14 J
e) +18 J

17. What is the coefficient of kinetic friction between the 4 kg block and the surface below?
a) 0.35
b) 0.30
c) 0.25
d) 0.20
e) 0.15

Expert

Intro: a solid ball of radius rb has a uniform charge density ρ. part a: what is the magnitude of the electric field e(r) at a distance r> rb from the center of the ball? express your answer in terms of ρ, rb, r, and ϵ0. part b: what is the magnitude of the electric field e(r) at a distance r express your answer in terms of ρ, rb, r, and ϵ0. part c: let e(r) represent the electric field due to the charged ball throughout all of space. which of the following statements about the electric field are true? check all that apply. e(0) = 0 e(rb)=0 limr→∞e(r)=0 the maximum electric field occurs when r=0 the maximum electric field occurs when r=rb the maximum electric field occurs as r→∞.