Blocks A and B rest on a horizontal surface. The coefficients of static and kinetic friction are μs=0.4, μk=0.3 for both contact surfaces. Determine the acceleration of each block if P=60 lb.



aA=9.66 ft/s2, aB=21.3 ft/s2

A man with weight of 150 lb is holding to a balloon with both hands equally. Determine the tension in each of his hands when: a) the balloon rises with v=0.8t ft/s, and b) the balloon descents with v=0.4t ft/s.

a) T=76.9 lb, b) T=74.1 lb

Problem 13.50

A freight elevator, including its load, has a mass of 1 Mg. It is prevented from rotating due to the track and wheels mounted along its sides. The motor M develops a constant tension T = 4.9 kN in its attached cable. Neglect the mass of the pulleys and cables.

Part A

Determine the velocity of the elevator when it has moved upward 4 m starting from rest.

Express your answer to three significant figures and include the appropriate units.

v =

6.25 ms

Problem 13.38

The 300-kg bar B, originally at rest, is being towed over a series of small rollers. The motor M is drawing in the cable for a short time at a rate of v=(0.4t2) m/s, where t is in seconds (0≤t≤6 s). Neglect the mass of the cable, pulley, and the rollers

Part A

Determine the force in the cable when t = 3 s .

Express your answer to three significant figures and include the appropriate units.

T =

0.720 kN

Part B

How far does the bar move in 3 s ?

Express your answer to three significant figures and include the appropriate units.

s =

3.60 m

Problem 13.1

The 3 lb particle is subjected to the action of its weight and forces F1={2i+6j−2tk}lb, F2={t2i−4tj−1k}lb, and F3={−2ti}lb, where t is in seconds. 

Part A

Determine the distance the ball is from the origin 2 s after being released from rest.

Express your answer to three significant figures and include the appropriate units.

s =

138 ft