Vectors & Relative Motion

1. Vectors & Relative Motion Multiple-Choice Practice Problems

2. Question #1 In a diagram, the length of a vector arrow represents the • type of vector. • direction of the vector. • magnitude of the vector. • cause of the vector.

3. Question #2 Which of the following quantities used to describe motion is an example of a vector quantity? • distance • speed • time • average velocity

4. Question #3 A vector remains unchanged • if it is moved in any direction. • only if it is moved parallel to its original direction. • only if it is rotated perpendicular to its original direction. • only if it is not moved.

5. Question #4 Which of these displacementswill be equal to d1 +d2 +d3? • d3+d4+d1 • d2+d1+d3 • d2+d4+d3 • d4+d3+d1

6. Question #5 Which of the following represents the vector resulting in the subtraction of d2 −d1 shown in the figure?

7. Question #7 If vectors are moved according to the rules of the triangle method of vector addition, then the resultant vector is drawn • from the tail of the first vector to the tail of the last vector. • from the tail of the first vector to the tip of the last vector. • from the tip of the first vector to the tail of the last vector. • from the tip of the first vector to the tip of the last vector.

8. Question #8 A skier slides onto a horizontal patch of slushy snow at velocity vskier, and slows to a constant speed without changing direction. Which of the following could be the skier’s resulting velocity? • -3vskier • +(1/4)vskier • -(1/5)vskier • all of the above.

9. Question #11 In a school playground, a child runs 5 m in the xdirection and then 2.0 m in the –y direction. Which of the following represents the magnitude of the child’s displacement?

10. Question #12 In the triangle below, what does Θequal?

11. Question #13 The projection of a vector along the axes of a coordinate system is • a component of the vector. • a tangent of the vector. • the resultant of the vector. • the magnitude of the vector.

12. Question #14 The components of a vector are • each equal to half the magnitude of the vector. • independent of the orientation of the vector. • perpendicular. • scalar quantities.

13. Question #15 A vector that has components that lie along the -x-axis and the +y-axis is oriented at angle A measured counterclockwise from the +x-axis. Which of these ranges gives values of A? • 0°<A<90° • 90°<A<180° • 180°<A<270° • 270°<A<360°

14. Question #16 If the x-component of B equals the magnitude of B, then • both components are equal. • Byequals B2+Bx2 • By equals zero. • By lies along the y-axis.

15. Question #17 Which of the following is a frame of reference for measuring motion? • coordinate system • diagram • graph • none of the above

16. Question #18-22 Story In a circus parade, a clown standing on a float moving at a constant forward speed drops a fake dumbbell. A child in the bleachers on the sidewalk observes the dumbbell falling.

17. Question #18 Who would observe the dumbbell falling straight down? • The clown only • The child only • The clown and the child • Neither

18. Question #19 Who would observe the dumbbell falling backward? • The clown only • The child only • The clown and the child • Neither

19. Question #20 The clown and child would agree about which of the following? • The time for the dumbbell to fall • The distance the dumbbell falls • The initial velocity of the dumbbell • All of the above

20. Question #22 If the float has a velocity of +vfloat with respect to the ground, what is the velocity of the child with respect to the clown? • 0 • +vfloat • -vfloat • (+vfloat–vchild)/2

21. Question #23 The velocity of a passenger relative to a boat is -vpb. The velocity of the boat relative to the river is +vbr. The velocity of the river to the shore is +vrs. What is the velocity of the passenger relative to the shore? • -vpb+vbr+vrs • vpb- (vbr+ vrs) • -(vpb + vbr+ vrs) • vpb+vbr+vrs

22. Question #24 A car traveling at the speed limit has velocity +vcarwith respect to the road. You are in another car traveling in the opposite direction at the speed limit with respect to the road. As the first car approaches you, what is its velocity relative to you? • +vcar • vcar • +2vcar • -2vcar

23. ANSWERS • 1: C • 2: D • 3: B • 4: B • 5: D • 7: B • 8: B • 11: D • 12: A • 13: A • 14: C • 15: B • 16: C • 17: A • 18: A • 19: D • 20: D • 22: C • 23: A • 24: C