Physics 1 Questions & Answers

Physics 1 Questions & Answers 2 identical molecules, A and B, move with the same horizontal velocities but opposite vertical velocities. Which of the following statements must be true after the 2 molecules collide? A. The sum of the KE of the molecules before the collision is at least as large as the sum of the KE of the molecules after the collision. B. Molecule A will have a greater momentum after the collision than molecule B will. C.The sum of the KE of the molecules after the collision is greater than the sum of the KE of the molecules before the collision. D. Molecule A will have a greater vertical velocity than molecule B will. - ANSWER: A. The sum of the KE of the molecules before the collision is at least as large as the sum of the KE of the molecules after the collision. A 1,000kg rocket ship, traveling at 100m/s, is acted on by an average force of 20kN applied in the direction of its motion for 8s. What is the change in velocity of the rocket? - ANSWER: 160m/s F=ma so a=F/m, a=v/t, v=at=Ft/m A 1,00kg satellite traveling at speed v maintains an orbit of radius, R, around the earth. What should be its speed if it is to develop a new orbit of radius 4R? A. 1/4v B. 1/2v C. 2v D. 4v - ANSWER: A. 1/4v GMM/r^2=Mv^2/r A 100kg elevator, starting at rest, accelerates up at rate, a. What is the average force acting on the elevator if it covers a distance, x, over a period of 10s? A. 2x+1000 B. 100(a+1) C. 2a+1000 D. 2ax - ANSWER: A. 2x+1000 ma=F-mg implies F=m(a+g) x=1/2at^2 implies a=2x/t^2 A 10kg wagon rests on a frictionless inclined plane. The plane makes an angle of 30 with the horizontal. What is the force, F, required to keep the wagon from sliding down the plane? A. 10N B. 30N C. 49N D. 98N - ANSWER: C. 49N