University of St. La Salle - Bacolod City

• PHYSICS 754

• Physics Key 1. B. im2 /s 3 Convert the given variables into their respective SI units wherein s, d, and y arerepresented in meters (m); t is represented in seconds (s), and a is representedinmeters per second squared (m/s 2 ). Then, isolate variable e. 2. D. time it takes for the egg to come to rest The softness of the pillow allows it to absorb the impact of the egg by prolongingthetime it takes for the egg to come to rest. 3. B. 295 edi/wow2 Apply dimensional analysis wherein 1 edi: 13.67m and 1 wow: 28.41s. Take in mindthat the final unit is m/s 2. 5.00m/s 2 (1 edi/ 13.67m) ((28.41s)2 /1 wow2 ) 4. A. It produces a torque with the star as the axis of rotation. A force whose direction goes through the axis of rotation always has a torque of zero. 5. C. decreases then increases Throughout the motion, the ball experiences a negative acceleration due to gravity. Initially, the ball’s movement is directed upwards (opposite the acceleration of gravity); hence, decreasing its speed. As the ball comes down, its speed is now in the samedirection as the acceleration due to gravity; thus, increasing its speed. 6. C. the gravitational force exerted by the can on Earth Option A is the reaction force to the force exerted by the can on the table. OptionBisthe same force as the given; hence it cannot be its own reaction force. Option Disthereaction force to the normal force exerted by the table on the can. 7. C. 31.0 m/s, toward east Both cars are moving relative to the ground (Earth: denoted as E) Relative velocityiscomputed by VBR =VBE — VER . Take note that VER= -17 since the direction is westward. A. 0.50 s B. 1.0 s C. 2.0 s D. 4.0 s 香䁞䀀㌳䁏䁞 ꀀ 䁞䁞 ব香ರ㌳䥜 ꀀ ꜜ香Āರ ㌳䁞 th t th 䁞 ꀀ th ㌳ ㌳ ꀀ hth 8. A force F is applied perpendicular to a rod at a distance L away fromthe axis of rotation. Which of the following is TRUE about the torque on the rod? A. Torque is parallel to force F B. The longer the lever arm, the smaller the torque. C. When the magnitude of F is doubled, the torque is halved. D. Torque is perpendicular to the lever arm. Torque and force are always perpendicular to the rod but are not parallel to eachother. 9. You toss a stone of mass m straight upward with kinetic energy K. If the stone reacheda maximum height h, what is its kinetic energy when it is at a height of h=4? A.¾ K B.⅜ K C.¼ K D. ½ K Total energy = K Maximum height = h Law of conservation of energy: ꀀ Đ䁞䁞 ꀀ 䁞tᆘ. At any point of time/height, Đ Đ ꀀ ꀀ Đ䁞䁞 . Thus, 䁞tᆘ ꀀ 䁞t ᆘ Đ. Đ ꀀ 䁞tᆘ 䁞tᆘ ꀀ Đ ꀀ 10. A. U = k|x| A point is in the position of stable equilibrium if the potential energy has a minimumat that point. The graphs of choices B and D are a downward parabola and thus will haveamaximum but not a minimum. The g