Quiz A ball is dropped from a tower
Quiz A ball is dropped from a tower and attains a speed v at the bottom. To achieve a speed 2 v at the bottom, how many times as high must the new tower be?
First Newton’s Law Second Newton’s Law Third Newton’s Law
No push Time of push 83 kg No push = Eugenia's 52 kg mass with gear David's mass with gear ≈ 0. 5 sec v. E ≈ 0. 9 m/sec v. D≈ 0. 55 m/sec m. Dv. Df ≈ - m. Ev. Ef a. D a. E
No push Time of push ≈ 0. 5 sec No push = Eugenia's mass with gear m. E David's mass with gear m. Dv. Df ≈ - m. Ev. Ef v. Df a. D a. E m. D(v. Df – v. Di)/t = FEon. D = - FDon. E = - m. E(v. Ef – v. Ei)/t m. D(v. Df – v. Di)/t = - m. E(v. Ef – v. Ei)/t m. Dv. Df – m. D v. Di = - (m. Ev. Ef – m. Ev. Ei)
p = mv ∑p = ∑ mv Units! momentum of a system
No push Time of push ≈ 0. 5 sec No push = Eugenia's mass with gear m. E David's mass with gear m. Dv. Df ≈ - m. Ev. Ef p. Df ≈ - p. Ef ∑mvi = ∑mvf v. Ef v. Df a. D a. E m. Dv. Df – m. D v. Di = - ( m. Ev. Ef – m. Ev. Ei) p. Df – p. Di = - (p. Ef – p. Ei) p. Di + p. Ei = p. Df + p. Ef
vis viva – living force Mv 2=const Gottfried Wilhelm Leibniz momentum – quantity of motion Mv=const René Descartes Isaac Newton
The momentum of a freely falling ball is not conserved. Why is this not a violation of the law of conservation of momentum?
No Homework
momentum p = mv Vi=0 F=const Quiz The block of mass m = 500 g is at rest on a frictionless surface. You start pulling the block with a constant force F = 10 N and pull it for t=2 sec. Find the final velocity of the block and its final momentum.
- Slides: 10