1 Marks Question

Question 11 Mark

Is a vector necessarily changed if it is rotated through an angle?

Answer

Not necessarily, a vector changes if it is rotated through any angle except for $2\pi,4\pi,6\pi, \ ...$ radians”

Question 21 Mark

If $\vec{\text{A}}=2\vec{\text{i}}+3\vec{\text{j}}+4\vec{\text{k}}$ and $\vec{\text{B}}=4\vec{\text{i}}+3\vec{\text{j}}+2\vec{\text{k}},$ find $\vec{\text{A}}\times\vec{\text{B}}.$

Answer

$\vec{\text{A}}=2\hat{\text{i}}+3\hat{\text{j}}+4\hat{\text{k}},\vec{\text{B}}=4\hat{\text{i}}+3\hat{\text{j}}+2\hat{\text{k}}$

$\vec{\text{A}}\times\vec{\text{B}}=\begin{vmatrix}\hat{\text{i}}&\hat{\text{j}}&\hat{\text{k}}\\2&3&4\\4&3&2\end{vmatrix}$

$\Rightarrow\hat{\text{i}}(6-12)-\hat{\text{j}}(4-16)+\hat{\text{k}}(6-12)=-6\hat{\text{i}}+12\hat{\text{j}}-6\hat{\text{k}}$

View full question & answer→

Question 31 Mark

The length of the string of a simple pendulum is measured with a metre scale to be 90.0cm. The radius of the bob plus the length of the hook is calculated to be 2.13cm using measurements with a slide callipers. What is the effective length of the pendulum? (The effective length is defined as the distance between the point of suspension and the centre of the bob.)

Answer

As shown in the figure,
Actual effective length = (90.0 + 2.13)cm
But, in the measurement 90.0cm, the no. of significant digits is only 2.
So, the addition must be done by considering only 2 significant digits of each measurement.
So, effective length = 90.0 + 2.1 = 92.1cm.

View full question & answer→

Question 41 Mark

Can we have physical quantities having magnitude and direction which are not vectors?

Answer

Yes, Electric current is such quantity that has got both magnitude and direction but is not a vector.

View full question & answer→

Physics 1 Marks Question

Test yourself on this topic