Question

Question 9 16 pts Two crates, m1 = 20 kg and m2 - 8 kg are in contact with each other on a horizontal, frictionless surface as shown in the figure. A pushing force, P, of 80 N acts on my, at an angle of 20° below the horizontal, but both crates accelerate together, along the ground. a) Draw a free body diagram for each crate. Clearly indicate which forces, if any, are Newton's 3rd law pair forces. b) Find the magnitude of the acceleration of the crates. P 20° m m2 Upload Choose a File

Answer 1

#Solution - P=80N Crate-1 crate-2 20 m, = 20kg / m₂ = 8k| (fig. 2) (a). Free body diagrams, N Px= P60$20 R R mong ry force (ie Py=psimbol Mag: (fig. 2.) (fig-3). where, Px = horigem tal component of the applied force. Cie. PCo820) vertical component of the applied (ie. psin20) Ni normal reaction force of Crate-1. mig = weight of the Crate-1: weight of the crate-2 H₂ = normal reaction force of Crate-2. R Reaction force between crate-1 and crate. ( Newton 3rd law). mag

(b). From Newton's and law 1 Px - R = my a Ni = Pyt mig And, R = mza H₂ = mag 7 from equation ② and ③. we get- (Px-R)+R (ma) +(m2a) Px (m, tm) a Py mitme a = as p cos 20° (20+8) a = 80 x 608209 28 = 80 x 0.94 28 a 75.2 28 a= 2.6857 la ñ 2.7 m/ seer Ane 그 Hence, the magnitude of the accel" of the crates will be 2.7 m/sec?