If and , then the scalar and vector products of and have the magnitudes respectively as
- A10, 2
- B5,
- C4,
- D10,
View written solutionFree
Correct answer: D
Given, $$\overrightarrow F = 2\widehat i + \widehat j - \widehat k$$ and $$\overrightarrow r = 3\widehat i + 2\widehat j - 2\widehat k$$
$$\overrightarrow F \,.\,\overrightarrow r = 2(3) + 2(1) + ( - 2)( - 1)$$
$ = 6 + 2 + 2 = 10$
$$\overrightarrow F \times \overrightarrow r = \left| {\begin{matrix} {\widehat i} & {\widehat j} & {\widehat k} \\ 2 & 1 & { - 1} \\ 3 & 2 & { - 2} \\
\end{matrix} } \right|$$
$$ = \widehat i( - 2 + 2) - \widehat j( - 4 + 3) + \widehat k(4 - 3)$$
$$ \Rightarrow \overrightarrow F \times \overrightarrow r = \widehat j + \widehat k$$
$$|\overrightarrow F \times \overrightarrow r | = \sqrt {{1^2} + {1^2}} = \sqrt 2 $$
More from Laws of Motion
- In the diagram shown, the normal reaction force between 2 kg and 1 kg is (Consider the surface, to be smooth) : (Given g = 10 ms2) Includes diagram2022 · MCQ
- Two bodies of mass 4 kg and 6 kg are tied to the ends of a massless string. The string passes over a pulley which is frictionless (see figure). The acceleration of the system in terms of acceleration due to gravity (g) is : Includes diagram2020 · MCQ
- A block of mass 10 kg is in contact against the inner wall of a hollow cylindrical drum of radius 1 m. The coefficient of friction between the block and the inner wall of the cylinder is 0.1. The minimum angular velocity needed for the…2019 · MCQ
- A mass m is attached to a thin wire and whirled in a vertical circle. The wire is most likely to break when :2019 · MCQ
- Which one of the following statements is incorrect?2018 · MCQ
- A block of mass m is placed on a smooth inclined wedge ABC of inclination q as shown in the figure. The wedge is given an acceleration ‘a’ towards the right. The relation between a and q for the block to remain stationary on the wedge is Includes diagram2018 · MCQ
- One end of string of length is connected to a particle of mass 'm' and the other end is connected to a small peg on a smooth horizontal table. If the particle moves in circle with speed '', the net force on the particle…2017 · MCQ
- Two blocks A and B of masses 3m and m respectively are connected by a massless and inextensible string. The whole system is suspended by a massless spring as shown in figure. The magnitudes of acceleration of A and B immediately after the… Includes diagram2017 · MCQ