HW8-solutions - Agha(sa9896 – HW8 – bohm –(59970 1...

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

View Full Document Right Arrow Icon

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

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Agha (sa9896) – HW8 – bohm – (59970) 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 10.0 points A plane designed for vertical takeoff has a mass of 7 . 6 × 10 3 kg. Find the net work done on the plane as it accelerates upward at 1.7 m/s 2 through a distance of 33.5 m after starting from rest. Correct answer: 4 . 3282 × 10 5 J. Explanation: Basic Concept: W net = F net d cos θ = F net d since θ = 0 ◦ ⇒ cos θ = 1. Given: m = 7 . 6 × 10 3 kg a net = 1 . 7 m / s 2 d = 33 . 5 m Solution: W net = F net d = ma net d = (7600 kg) ( 1 . 7 m / s 2 ) (33 . 5 m) = 4 . 3282 × 10 5 J 002 10.0 points A cart loaded with bricks has a total mass of 8 . 49 kg and is pulled at constant speed by a rope. The rope is inclined at 29 . 5 ◦ de- grees above the horizontal and the cart moves 19 . 8 m on a horizontal floor. The coefficient of kinetic friction between ground and cart is . 648. The acceleration of gravity is 9 . 8 m / s 2 . How much work is done on the cart by the rope? Correct answer: 0 . 781135 kJ. Explanation: F 2 9 . 5 ◦ Summing the components of the forces along the vertical direction provides summationdisplay F y = F sin θ + N - mg = 0 From this, N = mg- F sin θ For the horizontal direction we have summationdisplay F x = F cos θ- μ k N = 0 F cos θ- μ k ( mg- F sin θ ) = 0 Solving for F gives F = μ k mg μ k sin θ + cos θ . Since μ k sin θ + cos θ = (0 . 648) sin29 . 5 ◦ + cos 29 . 5 ◦ = 1 . 18945 , F = . 648(8 . 49 kg) (9 . 8 m / s 2 ) 1 . 18945 F = (45 . 3277 N) The work done on the cart is given by W F = F d cos θ = (45 . 3277 N) (19 . 8 m) cos 29 . 5 ◦ = 0 . 781135 kJ . 003 10.0 points A racing car has a mass of 1800 kg. The acceleration of gravity is 9 . 8 m / s 2 . What is its kinetic energy if it has a speed of 130 km / h? Correct answer: 1 . 17361 × 10 6 J. Explanation: Kinetic energy is K = 1 2 mv 2 = 1 2 (1800 kg) × parenleftBig 130 km h · 1000 m 1 km · 1 h 3600 s parenrightBig 2 = 1 . 17361 × 10 6 J . Agha (sa9896) – HW8 – bohm – (59970) 2 004 10.0 points Five ramps lead from the ground to the second floor of a workshop, as sketched below. All five ramps have the same height; ramps B, C, D and E have the same length; ramp A is longer than the other four. You need to push a heavy cart up to the second floor and you may choose any one of the five ramps....
View Full Document

Page1 / 6

HW8-solutions - Agha(sa9896 – HW8 – bohm –(59970 1...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online