Conceptual Questions Chapter 2 Vectors & Equilibrium l First Year Physics Federal Board KPK Syllabus

Описание: 1. Two vectors lie with their tails at the same point. When the angle between them is increased by 20o their scalar product has the same magnitude but changes from positive to negative. The original angle between them was:
A. 0 B. 60o C. 70o D. 80o
2. The minimum number of vectors of unequal magnitude required to produce a zero resultant is
A. 2 B. 3 C. 4 D. 5
3. If the resultant of two vectors, each of magnitude A is also a magnitude of A. the angle between the two vectors will be:
A. 30o B. 45o C. 60o D. 120o
4. The magnitude of vector A=2i ̂+j ̂+2k ̂ is
A. 9 B. 5 C. 3 D. 1
5. When Fx = 3 N and F= 5 N then Fy=
A. 6 N B. 4 N C. 2 N D. 0 N
6. A meter stick is supported by a knife-edge at the 50-cm mark. Arif hangs masses of 0.40 kg and 0.60 kg from the 20-cm and 80-cm marks, respectively. Where should Arif hang a third mass of 0.30 kg to keep the stick balanced?
A. 20 cm B. 70 cm C. 30 cm D. 25 cm
7. If Ax = 1.5 cm, Ay = –1.0 cm, into which quadrant do the vector A point?
A. I B. II C. III D. IV 8. A ⃗ · (A ⃗ × B ⃗) = ?
A. 0 B. 1 C.AB D.A2B
9. Two forces of magnitude 20 N and 50 N act simultaneously on a body. Which one of the following forces cannot be a resultant of the two forces?
A. 20 N B. 30 N C. 40 N D. 70 N
10. If the dot product of two nonzero vectors A and B is zero then the magnitude of their cross product is __
A. 0 B. 1 C. AB D. –AB
11. The sum of magnitudes of two forces is 16N. If the resultant force is 8N and its direction is perpendicular to minimum force then the forces are
A. 6N and 10N B. 8N and 8N C. 4N and 12N D. 2N and 14N
12. Find the mass of the uneven rod shown in the figure. If its center of gravity is 14 cm from end A is ____
A. 100 g

B. 150 g

C. 80 g

D. 5 g

13. The following diagrams show a uniform rod with its midpoint on the pivot. Two equal forces F are applied on the rod, as shown in the Figure. Which diagram shows the rod in equilibrium?






14. For which angle the equation |A ⃗.B ⃗ |=|A ⃗.B| is correct.
A. 30o B. 45o C. 60o D. 90o
15. What is the net torque on wheel radius 2 m as shown?
A. 10 N anticlockwise

B. 10 Nm anticlockwise

C. 10 Nm clockwise

D. 5 Nm clockwise

Give a short response to the following questions
1. Is it possible to add three vectors of equal magnitude but different directions to get a null vector? Illustrate with a diagram.
2. The magnitudes of three vectors are 2m, 3m, and 5m, respectively. The directions are at your disposal. Can these three vectors be added to yield
zero? Illustrate with a diagram.
3. What units are associated with the unit vectors i ̂, j ̂, and k ̂ ?
4. Can a scalar product of two vectors be negative? Provide a proof and give an example.
5. A and B are two nonzero vectors. How can their scalar product be zero? And how can their vector product be zero?
6. Suppose you are given a known nonzero vector A. The scalar product of A with an unknown vector B is zero. Likewise, the vector product of A with B is zero. What can you conclude about B?
7. Why a particle experiencing only one force cannot be in equilibrium?
8. To open a door that has the handle on the right and the hinges on the left a torque must be applied. Is the torque clockwise or counterclockwise when viewed from above? Does your answer depend on whether the door opens toward or away from you?
9. Explain the warning ‘Never use a large wrench to tighten a small bolt’.
10. A central force is one that is always directed toward the same point. Can a central force give rise to a torque about that point?