Jim and Mary are carrying Bob on a horizontal stretcher.The uniform stretcher is 2.00 m long and weighs 80 N.Bob weighs 600 N.Bob's center of gravity is 80 cm from Mary.Jim and Mary are at the ends of the stretcher.The force that Jim is exerting to support the stretcher,with Bob on it,is
A) 280 N.
B) 320 N.
C) 380 N.
D) 400 N.
E) 520 N.

Question

Quizplus · Accepted Answer

To find the force Jim is exerting, we can use the principle of moments (torque). Taking moments about Mary's end, the total moment due to Bob and the stretcher must equal the moment due to Jim's force. Bob's weight (600 N) acts 0.8 m from Mary, and the stretcher's weight (80 N) acts at its center, 1 m from Mary. The equation is: (600 N * 0.8 m) + (80 N * 1 m) = Jim's force * 2 m. Solving gives Jim's force as 280 N.

Jim and Mary Are Carrying Bob on a Horizontal Stretcher