{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Homework 27

# Homework 27 - sanchez(ds28677 homework 27 Turner(58220 This...

This preview shows pages 1–3. Sign up to view the full content.

sanchez (ds28677) – homework 27 – Turner – (58220) 1 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points An 11 m ladder whose weight is 337 N is placed against a smooth vertical wall. A person whose weight is 342 N stands on the ladder a distance 4 . 4 m up the ladder. The foot of the ladder rests on the floor 4 . 62 m from the wall. 342 N 337 N 4 . 4 m 11 m 4 . 62 m Note: Figure is not to scale. Calculate the force exerted by the wall. Correct answer: 141 . 292 N. Explanation: Let : = 11 m , d = 4 . 4 m , s = 4 . 62 m , W = 337 N , and W p = 342 N . Pivot N w F f N f W p W θ θ = arccos s = arccos parenleftbigg 4 . 62 m 11 m parenrightbigg = 65 . 1654 In equilibrium summationdisplay vector F = 0 and summationdisplay vector τ = 0 . summationdisplay τ : W p d cos θ + W 2 cos θ N w sin θ = 0 , where d is the distance of the person from the bottom of the ladder. Therefore 2 F w sin θ = 2 W p d cos θ + W cos θ F w = 2 W p d + W 2 cos θ sin θ = 2 (342 N)(4 . 4 m) + (337 N)(11 m) 2 (11 m) × cos 65 . 1654 sin 65 . 1654 = 141 . 292 N . 002 (part 2 of 2) 10.0 points Calculate the normal force exerted by the floor on the ladder. Correct answer: 679 N. Explanation: Applying translational equilibrium, summationdisplay F y : N f − W p − W = 0 N f − W p − W = 0 . N f = W p + W = 342 N + 337 N = 679 N .

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
sanchez (ds28677) – homework 27 – Turner – (58220) 2 003 (part 1 of 3) 10.0 points A 17 . 8 m , 481 N uniform ladder rests against a frictionless wall, making an angle of 68 . 3 with the horizontal. 767 N 481 N 5 . 82 m 17 . 8 m 68 . 3 Note: Figure is not drawn to scale. Find the horizontal force exerted on the base of the ladder by Earth when a 767 N fire fighter is 5 . 82 m from the bottom. Correct answer: 195 . 505 N. Explanation: Let : L = 17 . 8 m , δ = 5 . 82 m , α = 68 . 3 , W = 481 N , and W p = 767 N . L sin α L cos α L 2 cos α δ cos α Pivot N w f N g W p W Applying rotational equilibrium with the pivot at the point of contact with the ground, summationdisplay τ = W p δ cos α + W L 2 cos α −N w L sin α = 0 2 W p δ cos α + W L cos α = 2 N w L sin α N w = W p δ cos α L sin α + W cos α 2 sin α = W p δ L tan α + W 2 tan α = (767 N) (5 . 82 m) (17 . 8 m) tan 68 . 3 + 481 N 2 tan 68 . 3 = 195 . 505 N .
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}