Physics 211 Fall 2017 Midterm Exam #2 Name (Last, First): Student ID #: - Part I
ID: 1789229 • Letter: P
Question
Physics 211 Fall 2017 Midterm Exam #2 Name (Last, First): Student ID #: - Part II: Multiple choice problems, 4 points each, 48 points total. 1. The net force on a box is in the positive x direction. Which of the following statements best describes the motion of the box a. Its velocity is parallel to the x-axis b. Its acceleration is parallel to the x-axis c. Both its velocity and its acceleration are parallel to the x-axis d. Neither its velocity or its acceleration need be parallel to the x-axis stome on a frozen pond. The stone slides, slows down and eventually stops. 2. You kick a smooth You conclude that: a. the force that was pushing the stome forward finally stopped pushing it b. no net force acted on the stone c. a net force acted on it all the time while it was moving d. the stone has a natural tendency to be at rest 3. Two blocks of masses 20 kg and 8 kg are connected together by a light string and rest on a frictionless level surface. Attached to the 8-kg mass is another light string, which a person uses to pall both blocks horizontally. The two-block system accelerates to the right. T is tension in tcing on the 20-kg-box the string. Which would be a correet diagram of horizontal forces acting on the 20-kg-box? 4 A bop sts on an ielined plane without singAsthe nge of inclination increases, the the normal force acting on the box: a. increases in magnitude b. decreases in magnitude c. magnitude doese't change but it changes direction d. magnitude doesn't change and it always points upExplanation / Answer
1) (c) Both its velocity and acceleration are parallel to the x axis.
2) (c) A net force acted on it all the time while it was moving.
Its stopped when the net force became zero.
3) (b)
When you draw the forces on a body, only the immediate ones are taken into account, i.e. the ones directly acting upon it.
4) (b) decreases in magnitude
Normal force on an incline is proportional to cosine of the angle. So, as the angle increases, cosine of the angle decreases, thus normal force decreases.