# Physics

Topics: Force, Speed, Vector Motors Pages: 2 (419 words) Published: February 2, 2011
Mathematics and Physical Science Department Name: Student # Score: Rye Alfonso PHYSICS 103 LECTURE Recitation Activity #2 ANSWER KEY Chapter 2: MOTION in One-Dimension, VECTORS DIRECTION: Please show complete solutions and box all final answers. Write the answer up to two decimal places. ☺ 1. Three horizontal ropes pull on a large stone stuck in the ground, producing the vector forces , and given in the figure below. Find the magnitude and direction of a fourth force on the stone that will make the vector sum of the four forces zero. (5 points) Let be the fourth vector ,

Given that We have

Ax =+A cos 30° =100 cos 30°= +86.60 N Bx =-B sin 30° = -80 sin 30° = -40.00 N

Cx =-C cos 53°=- 40 cos 53° = -24.07 N
Dx= -(Ax+Bx+Cx)=-22.53 N (1 point) (1 point)

Ay =+A sin 30°=100 sin 30°= +50.00 N By =+B cos 30°=80 cos 30° = +69.28 N Cy =-C sin 53°= -40 sin 53°= -31.95 N Dy= -(Ay+By+Cy)=-87.33 N (1 point)

θ
counterclockwise from the – x- axis or S of W Or

α

counterclockwise from the + x- axis (2 points)

2. You are on the roof of the physics building, 46.0 m above the ground. Your physics professor, who is 1.80 m tall, is walking alongside the building at a constant speed of 1.20 m/s. If you wish to drop an egg on your professor’s head, where should the professor be when you release the egg? Assume that the egg is in free fall. (5 points)

BONUS: (3 points) Ranking Task: D. Maloney, Physics Ranking Tasks Pictured below are six waterfalls all of which have the same amount of water flowing over them. The waterfalls differ in height and in the speed of the water as it goes over the edge. The specific values of the heights and speeds are given in the figures. Rank these situations from longest to shortest based on how long it takes the water to go from the top of the falls to the bottom. That is, put first the situation where it takes the water the most time to go from the top of the falls to the bottom, and put last the one that takes the least time....