Ok, so we have a test using our homework problems, so I actually need them all done, so more this time lol. I am lost. I hate this teacher lol. Sorry for so many. If you manage to show me how to do any of these, I will + rep you. Thanks! 1. A bicyclist rides 5.0km due east, while the resistive force from the air has a magnitude of 3.0N and points due west. The rider then turns around and rides 5.0km due west, back to her starting point. The resistive force from the air on the return trip has a magnitude of 3.0N and points due east. (a) Find the work done by the resistive force during the round trip. (b) Based on your answer to part (a), is the resistive force a conservative force? Explain. (answer)- a. -3.0 x 10^4 J (b.) no 2. A 75.0 kg skier rides a 2830 m long lift to the top of a mountain. The lift makes an angle of 14.6 degrees with the horizontal. WHAT IS THE CHANGE IN THE SKIER'S GRAVITATIONAL POTENTIAL ENERGY? (answer)- 5.24 x 10^5 J 3. 47.0 g golf ball is driven from the tee with an initial speed of 52.0 m/s and rises to a height of 24.6 m. (a) Neglect air resistance and determine the kinetic energy of the ball at its highest point. (b) What is its speed when it is 8.0 m below its highest point? (answer)- (a)- KEf= 52.2 J (b) Vf= 48.8 m/s 4. a projectile mass of 0.750 kg is shot straight up with an intial speed of 18.0 m/s. (a) how high would it go if there were no air friction? (b) if the projectile rises to a max height of only 11.8 m, determine the magnitude of the avg force due to air resistance. (answer)- (a)- Hf= 16.5 m (b)- avg. Fa= 2.9 N 5. A golf ball strikes a hard smooth floor at an angle of 30 degrees and rebounds at the same angle. the mass of the ball is 0.047 kg, and its speed is 45 m/s just before and after striking the floor. what is the magnitude of the impulse applied to the golf ball by the floor? (answer)-3.7 N(s) 6. The earth and moon are separated by a center-to-center distance of 3.85 x 10^8 m. The mass of the earth is 5.98 x 10^24 kg and that of the moon is 7.35 x 10^22 kg. How far does the center of mass of the earth-moon system lie from the center of the earth? (answer) 4.67 x 10^6m Thanks again
Haven't done mech in over a year sooo....we'll see how this turns out. I'll add more as I solve them. #2 U = mgh U = (75)(9.8)(2830sin14.6) U = 524316.87 #3 Part a Part b too tired will finish in the morning
+ rep pando, for whatever reason, seeing what was done for the first two made things click in my head and i did the rest lol
Part (a) Work done by R. force when cyclist rides due east: 5.0 x 10^3 x (-3.0) = -1.5 x 10^-4 J Work done by R. force when cyclist rides due west: 5.0 x 10^3 x (-3.0) = -1.5 x 10^-4 J Therefore, total work done: 2 ( -1.5 x 10^-4 ) = -3.0 x 10^-4 J Part (b) No. This is because a conservative force is a force with the property that the work done in moving a particle between two points is independent of the path taken.* As the resistive force is dependent on the velocity of the cyclist, it is not a conservative force. (* Took this definition off Wikipedia xD) Part (a) m = 0.750 kg, u = 18.0 m/s, v = 0.0 m/s, a = 9.8 m/s², s = ? Taking upwards as positive, v² = u² + 2as 0.0² = 18² + 2(-9.8)(s) s = 16.5 m Part (b) Taking downwards as positive, v² = u² + 2(net a)s 0.0² = 18² + 2(net a)(11.8) net a = 13.73 m/s² Hence, acceleration due to air resistance = 13.73 - 9.8 = 3.93 m/s² F = ma F = 0.750 x 3.93 F = 2.9 N