The Sick Note
Irish Folk Song –
The Sick Note by the Dubliners (also known as Paddy is not at work today or The Bricklayers Song)
https://www.youtube.com/watch?v=YbkoXGhZlFI&index=1&list=PLj_dQkdzvwTDvytxYJy4tUzblhuEqI0Jg
Watch the video first, The scenario in this song will be the basis of the problem(s) that will follow.
Solving for Phase 1 (Paddy accelerates directly upward while the full barrel of bricks accelerates downward)
Paddy’s mass = 115 [kg], Mass of barrel = 20 [kg], Mass of bricks (enough to fill barrel) = 170 [kg], Vertical distance from top to bottom 54 [m], Speed of anything at the start of either phase = 0 [m/s].
PLEASE SHOW STEP BY STEP ON HOW YOU SOLVED FOR EACH PROBLEM BELOW: MUST BE CLEAR AND EASY TO UNDERSTAND
Among the possible quantities that you could be asked to solve for would be
– The tension in the rope when Paddy shoots up like a rocket,
– Paddys acceleration when he shoots up like a rocket,
– The speed with which Paddy hits the pulley,
– The force of impact from the pulley while Paddy is being slowed down due to impact,
– The tension in the rope when Paddy accelerates downward,
– Paddys acceleration when he accelerates downward,
– The speed with which Paddy hits the ground,
– The speed with which the bricks hit Paddy.
Tips:
The mass of the barrel and bricks must be larger than the mass of Paddy initially and then, once half of the bricks are lost, the mass of the barrel and remaining bricks must be less than Paddys mass. In order to maximize the acceleration initially, the difference in masses between Paddy and the barrel+bricks needs to be maximized. As a result, the acceleration once half of the brakes have spilled out will be minimized.
Common conceptual difficulties involve mis-matching the masses and net forces associated with
Newtons 2nd Law. Take the time to emphasize the system definition piece of the problem-solving process.
A typical, logical and well-defined problem-solving structure will require simultaneous solutions involving equations with multiple (similar) unknowns. Think substitution.
