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Conservation of the energy

# Conservation of the energy - adamkiewicz(ja28724...

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adamkiewicz (ja28724) – Conservation of the energy – Morozova – (11102) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Starting from rest at a height equal to the radius of the circular track, a block of mass 16 kg slides down a quarter circular track under the influence of gravity with friction present (of coefficient μ ). The radius of the track is 51 m. The acceleration of gravity is 9 . 8 m / s 2 . 51 m 16 kg θ If the kinetic energy of the block at the bottom of the track is 2600 J, what is the work done against friction? Correct answer: 5396 . 8 J. Explanation: W = W f + K W f = m g R - K = (16 kg) (9 . 8 m / s 2 ) (51 m) - (2600 J) = 5396 . 8 J . 002 10.0 points A spring with a force constant of 5.5 N/m has a relaxed length of 2.62 m. When a mass is attached to the end of the spring and allowed to come to rest, the vertical length of the spring is 3.69 m. Calculate the elastic potential energy stored in the spring. Correct answer: 3 . 14848 J. Explanation: Given: k = 5 . 5 N / m x = 3 . 69 m - 2 . 62 m = 1 . 07 m Solution: U elastic = 1 2 kx 2 = 1 2 (5 . 5 N / m)(1 . 07 m) 2 = 3 . 14848 J 003 (part 1 of 6) 10.0 points A projectile of mass 0 . 522 kg is shot from a cannon, at height 6 . 9 m, as shown in the figure, with an initial velocity v i having a horizontal component of 5 . 9 m / s. The projectile rises to a maximum height of Δ y above the end of the cannon’s barrel and strikes the ground a horizontal distance Δ x past the end of the cannon’s barrel. Δ x v i 57 Δ y 6 . 9 m Determine the vertical component of the initial velocity at the end of the cannon’s bar- rel, where the projectile begins its trajectory.

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