Vector Practice Test 1 ( Addition and Resolution of Vector )
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1 / 38
Unit vector along the vector 4î + 3ĵ is _____
Explanation:
Unit vector along 4î + 3ĵ , is obtained by dividing the present vector by its magnitude.
The magnitude of the given vector is 5. Hence, the required unit vector is (4î + 3ĵ)/5.
2 / 38
When two vectors in the same direction are added, the magnitude of resulting vector is equal to _______
Consider the graphical representation of these two vectors. When one vector is added to the other in the same direction, the lengths will be added.
The resultant vector will bear the resultant length. Length is the magnitude of the vector. Hence the magnitudes add to give the magnitude of the resultant vector.
3 / 38
Following sets of three forces act on a body. Whose resultant cannot be zero
For three forces to have zero resultant, their magnitudes must satisfy the triangle inequality.
(each pair’s sum ≥ the third).
Here 10 + 20 = 30 < 40, so they can’t form a closed triangle and cannot balance to zero.
4 / 38
When subtracting B = 4î + 2ĵ from A = î – 6ĵ, the resultant A – B is:
A – B = (î – 6ĵ) – (4î + 2ĵ)= î – 6ĵ – 4î – 2ĵ= (1 – 4)î + (–6 – 2)ĵ= –3î – 8ĵ
5 / 38
If u and v are perpendicular unit vectors, then |u – v| equals:
|u| = |v| = 1 (unit vectors)Angle between u and v = 90° (perpendicular)
Use the formula:|u − v|² = |u|² + |v|² − 2|u||v|cosθ
= 1² + 1² − 2(1)(1)cos(90°)= 1 + 1 − 0= 2
Therefore,|u − v| = √2
6 / 38
A plane flies 300 km due north and then 400 km due west. Its resultant displacement is:
R = √(300² + 400²) = 500 km.
7 / 38
Two vectors of equal magnitude V with angle 60° to each other. The magnitude of their resultant is:
R = √(V² + V² + 2·V·V·cos 60°) = √(2V² + 2V²·½) = √(2V² + V²) = √(3V²) = V√3
8 / 38
If A = 7î + 24ĵ, the magnitude of A is:
|A| = √(7² + 24²) = √(49 + 576) = √625 = 25.
9 / 38
Two equal forces P each act at a point with an angle of 120° between them. The magnitude of their resultant is:
We know:cos(120°) = -1/2
So,R = √[2P² + 2P²·(-1/2)]R = √[2P² - P²]R = √[P²]R = P
10 / 38
If the sum of two unit vectors is a unit vector, then the magnitude of their difference and the angle between them are, respectively:
Let the two unit vectors be A and B.So,|A| = |B| = 1|A + B| = 1
Use the formula:|A + B|² = |A|² + |B|² + 2|A||B|cosθ
⇒ 1² = 1² + 1² + 2(1)(1)cosθ⇒ 1 = 1 + 1 + 2cosθ⇒ 1 = 2 + 2cosθ⇒ 2cosθ = -1⇒ cosθ = -1/2⇒ θ = 120°
Now, find |A − B|:|A − B|² = |A|² + |B|² − 2|A||B|cosθ= 1 + 1 − 2(1)(1)(cos120°)= 2 − 2(−1/2)= 2 + 1 = 3⇒ |A − B| = √3
11 / 38
At what angle should the two force vectors 5 N and 12 N be added to get a resultant of 13 N?
For resultant we use below formula:
12 / 38
Two equal forces F act at right angles on a point. The magnitude of their resultant is:
13 / 38
A particle moves 5 m east then 12 m north. Its resultant displacement from the start is:
14 / 38
The angle between vector Q and the resultant of (2Q + 2P) and (2Q – 2P)
(2Q + 2P) + (2Q – 2P) = 4Q, which is parallel to Q, so the angle between them is 0°.
15 / 38
Two perpendicular forces have magnitudes A and A/2. The magnitude of their resultant is:
16 / 38
When A = 2î + 3ĵ + 2k̂ is subtracted from B, the result is 2ĵ. The magnitude of B is:
B – A = 2ĵ ⇒ B = A + 2ĵ = 2î + (3+2)ĵ + 2k̂ = 2î + 5ĵ + 2k̂ ⇒ |B| = √(4+25+4) = √33.
17 / 38
A vector in the xy-plane makes an angle of 30° with the y-axis. Its y-component is 2√3. The magnitude of its x-component is:
18 / 38
Given A = (2, 3) and B = (–2, –3), the graphical sum A + B forms:
Plot A, then attach B head-to-tail; you return to the origin.
A and B are equal in magnitude but opposite in direction.
Their head-to-tail connection completes the path back to the start, you will get a straight line.
19 / 38
Which property of vector addition states A + B = B + A?
“Commutative” means order doesn’t matter.
Graphically, placing A then B, or B then A, yields the same head-to-tail resultant.
Magnitude and direction are identical either way.
This holds for all vectors in a vector space.
20 / 38
Which is not part of adding vectors by rectangular components?
Steps: (1) resolve into components, (2) add all x’s and all y’s, (3) recombine into R.
Parallelogram law is an equivalent graphical check.
At no point do you multiply components.
Option (d) is irrelevant to vector addition.
21 / 38
Two vectors A and B add to a resultant purely along the x-axis if:
Pure x-axis resultant means no net vertical component.
Component addition: Rᵧ = Aᵧ + Bᵧ must be zero.
Horizontal sum Aₓ + Bₓ can be nonzero.
Hence only condition (a) guarantees R is along x.
22 / 38
If A = 8î + 6ĵ and B = –8î + 6ĵ, the resultant A + B lies:
Sum x-components: 8 + (–8) = 0 → no horizontal part.
Sum y-components: 6 + 6 = 12 → positive vertical part.
Zero x and positive y ⇒ a vector straight up along +y.
23 / 38
Which method adds two vectors by drawing them from the same origin to form a parallelogram?
Parallelogram law uses the two vectors as adjacent sides.
The diagonal from the common origin is the resultant.
It decomposes into perpendicular components on x and y.
This visual proof also shows commutativity of addition.
24 / 38
A = 4î + 3ĵ and B = –2î + 6ĵ. What is the angle θ of R from the +x-axis?
Rₓ = 4 + (–2) Rₓ = 2, Ry = 3 + 6 Ry = 9.
θ = tan⁻¹(Ry/Rx) = tan⁻¹(9/2).
Compute components first, then use tan⁻¹.
This yields the correct direction of R.
25 / 38
A = 3î – 4ĵ, B = –5î + 2ĵ. The resultant A + B is:
Sum x-components: 3 + (–5) = –2 → –2î.
Sum y-components: –4 + 2 = –2 → –2ĵ.
R = –2î + (–2ĵ) by component-wise addition.
Vector closure ensures the result is itself a vector.
26 / 38
If Ax+ Bx= 0 but Ay + By ≠ 0, then A + B
Zero x-sum means no horizontal part; nonzero y-sum gives a pure vertical resultant.
27 / 38
Two equal-magnitude vectors at right angles are added. The resultant’s magnitude is V√2 because
If each component= V, then R = Vî + Vĵ use Pythagoras’ theorem ⇒ |R| = √(V² + V²) = V√2.
28 / 38
A = 5î + 0ĵ and B = 0î + 12ĵ. The magnitude of A + B is
R = (5+0)î + (0+12)ĵ = 5î + 12ĵ. Magnitude = √(5² + 12²) = 13.
29 / 38
Subtracting 2î + 7ĵ from î + ĵ gives ______
Subtract component-wise: (î+ĵ) – (2î+7ĵ) = (1–2)î + (1–7)ĵX-component: 1 – 2 = –1 → –îY-component: 1 – 7 = –6 → –6ĵ Resultant: –î –6ĵ
30 / 38
ding 2î + 7ĵ and î + ĵ gives ______
Add x-components: 2 + 1 = 3Add y-components: 7 + 1 = 8Result: 3î + 8ĵ
31 / 38
On adding two vectors we get _____
On adding two vectors we get a vector. Vector addition preserves both magnitude and direction. Use the head-to-tail or parallelogram law to find the resultant. Vectors are closed under addition, so the result is always another vector.
32 / 38
If u·v = 0 (and neither u nor v is the zero vector), then u and v are:
A dot product of zero indicates the vectors are orthogonal (at right angles).
33 / 38
The vector from P(1, 2, 3) to Q(4, 0, 5) is:
Subtract coordinates: (4–1)i + (0–2)j + (5–3)k = 3i – 2j + 2k.
34 / 38
A unit vector u satisfies u×i = j. Then u is:
35 / 38
If u and v are two perpendicular unit vectors, then |u + v| equals:
Since u·v=0 and |u|=|v|=1, |u+v| = √(u·u + 2u·v + v·v) = √(1+0+1) = √2.
36 / 38
Which property holds for any unit vector u?
By definition, a unit vector has magnitude 1, so its dot product with itself is |u|² = 1.
37 / 38
The unit vector parallel to a = 3 i – 4 j + 12 k is:
|a|=√(3²+ (–4)²+12² ) = √(9+16+144) =√169=13. So the unit vector is a/|a| = (3/13) i – (4/13) j + (12/13) k.
38 / 38
Which of the following is a unit vector?
The magnitude of i+j+k is √(1²+1²+1²)=√3. Dividing by √3 gives a vector of length 1:
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