TS EAMCET 2017 :: Physics :: General questions

• Physics - General questions

Consider  a particle  on which  constant forces $F_{1}=\hat{i}+2\hat{j}+3\hat{k}$ N and $F_{2}=4\hat{i}-5\hat{j}-2\hat{k}$ N act together resulting in a displacement from position  $r_{1}=20\hat{i}+15\hat{j}$ cm to $r_{2}=7\hat{k}$  cm. The  total work done on the particle is 

Answer:

Explanation:

Given, 

$F_{1}=\hat{i}+2\hat{j}+3\hat{k}$ N

$F_{2}=4\hat{i}-5\hat{j}-2\hat{k}$ N

$r_{1}=20\hat{i}+15\hat{j}$ cm

$r_{2}=7\hat{k}$  cm

Total  force on particle , $F= F_{1}+F_{2}$

               =$\hat{i}+2\hat{j}+3\hat{k}+4\hat{i}-5\hat{j}-2\hat{k}$

= $(5 \hat{i}-3\hat{j}+\hat{k})N$

 Displacement of pratice , $s=r_{2}-r_{1}$

= $7 \hat{k}-20\hat{i}-15\hat{j}$

  =$(-20 \hat{i}-15 \hat{j}+7\hat{k})$cm

 We know that,

Work (w)=F.s

 = $(5\hat{i}-3\hat{j}+\hat{k})(-20 \hat{i}-15 \hat{j}+7\hat{k}) \times 10^{-2}$

  =$(-100+45+7) \times 10^{-2}$

 =-0.48 J

A current-carrying wire in its neighbourhood produces

Answer:

Explanation:

A current-carrying conductor produces a magnetic field in its neighbourhood

The declaration of a car travelling on a straight highway is a function of its instantaneous velocity v given by $\omega=a\sqrt{v}$, where a is a constant. If the initial velocity of the car is 60 km/h, the distance of the car will travel and the time it takes before it stops  are 

Answer:

Explanation:

Deceleration $\omega=-a\sqrt{v}$

But   $\omega=\frac{dv}{dt}\Rightarrow\frac{dv}{dt}=-a\sqrt{v}$

$\frac{-dv}{\sqrt{v}}=a.dt\Rightarrow\int_{v_{i}}^{0} \frac{dv}{\sqrt{v}}=\int adt$

 $|2\sqrt{v}|_{v_{i}}^{0}=at\Rightarrow t=\frac{a}{2}\sqrt{v_{i}s}$

Again, 

$\frac{-dv}{dt}=a\sqrt{v}\Rightarrow\frac{dv}{dx}.\frac{dx}{dt}=-a\sqrt{v}$

$\frac{dv}{dx}.v=-a\sqrt{v}\Rightarrow dv \sqrt{v}=-a.dx$

 $\int_{v_{0}}^{0} \sqrt{v}dv=-a\int_{0}^{s} ds$

 After solving , we get

   $s=\frac{2}{3a}.v_{0}^{3/2}$

Which of the following statement is not true?

Answer:

Explanation:

The majority charge carriers in n-types semiconductor are electrons 

 A sound  wave of freequency v Hz  initially travels a distance of 1 km in air . Then , it gets reflected into a water reservoir  of depth 600 m. The frequency of the wave at the bottom of the reservoir is

 $(V_{air}=340 m/s, V_{water}=1484 m/s)$ 

Answer:

Explanation:

The frequency of sound wave remains constant

• Physics - General questions