(2) A force with magnitude 8.86 N pushes three boxes with masses m₁ = 1.30 kg, m2 = 3.20 kg, and m3 = 4.90 kg, as shown in the figure below. The surface the boxes are sliding on is so slippery that the surface can be considered to be frictionless. (a) Calculate the force that boxes 1 and 2 exert on each other and the force that boxes 2 and 3 exert on each other. [answer: F2-on-1 = F1-on-2 = 7.63 N; F3-on-2 = F2-on-3 = 4.62 N]. (b) To obtain the values of F1-on-2 and F3-on-2 in (a), you needed to assume that Newton's 3rd Law is valid. If you examine the FBD for m2, you should see that F1-on-2-F3-on-2= m2a. Verify the validity of Newton's 3rd Law by showing that the values of F1-on-2 - F3-on-2 and m2a are indeed equal. [answer: They are both equal to 3.0 N.] Fnet = ma F = 8.86 N 1.30 kg 3.20 kg t 4.90 kg

A 2 kg aluminum block and a 6 kg copper block are connected by a light string over a frictionless pulley. The two blocks are allowed to move on a fixed steel block wedge (of angle 6 = 35°) as shown in the Fig. (2). The coefficient of 25 kinetic friction for each block is shown in the figure. Determine: (a) The acceleration of the two blocks. (b) The tension in the string. Aluminum Copper H = 0.47 Steel H =0.36 Fig. 2 2.

(ex) Two masses, pulley, incline with friction, static vs. kinetic friction: The two blocks shown below are connected by a light string over a massless frictionless pulley. The coefficient of static friction between each block and surface is 0.35, and the coefficient of kinetic friction is 0.20. The mass of block A is 10.0 kg, and the mass of block B is unknown. The angle of the incline is 30 degrees. Do everything in symbols first substitute numbers in only at the end. (See PSL 5.5,7,8,9) a) The blocks are released from rest, and they are on the verge of sliding, but they do not move. Draw FBDs for each block. b) In symbols, solve for the mass of block B. (What else could you solve for?) c) Substitute the numbers to determine the mass of block B. A 0 B