First slide

Vectors

Question

The resultant of two vectors 3P and 2P is R. If the first vector is doubled, then the resultant is also doubled. The angle between the two vectors is

Moderate

A

60⁰
B

120⁰
C

90⁰
D

180⁰

Solution

Resultant, $R = \sqrt{9 P^{2} + 4 P^{2} + 12 P^{2} \cos θ}$ …(i)
$2 R = \sqrt{36 P^{2} + 4 P^{2} + 24 P^{2} \cos θ}$ …(ii)
Equating Eqs. (i) and (ii), we get
$\cos θ = - \frac{1}{2}$
$∴$ $θ = 120 °$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App