Tag: motion and rest

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Questions Related to motion and rest

Multiple choice physics motion and measurement of distances motion around us motion and rest moving things around us

Can a moving object cover zero distance?

  1. Always

  2. Sometimes

  3. Never

  4. Can't be said from given condition
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A moving object always changes its position. Then, it has move along a path with some length.
So, if the body is moving, it will always cover some path which can never have zero length. Thus distance travelled by a moving object can never be zero.

Multiple choice physics motion and measurement of distances motion around us motion and rest moving things around us

State whether given statement is True or False.
Path length is scalar Quantity ?

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Path length is distance covered by body in reaching from initial point to final point. It may be different for different paths.

Since path length is distance hence it is scalar quantity, it may be different for two paths with same initial and final points.

Multiple choice physics motion and measurement of distances motion around us motion and rest moving things around us

The distance of closest approach of an $\alpha $-particle projected towards a nucleus with momentum p is r. What will be the distance of closest approach, when the momentum of projected $\alpha $-particle is 2p?

  1. 2r

  2. 4r

  3. $\dfrac { r }{ 2 } $

  4. $\dfrac { r }{ 4 } $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

At the distance of closest approach:$KE=PE$

$\dfrac{p^2}{2m}=\dfrac{k 2 eq}{r}$
When the momentum chnages to 2p:
$\dfrac{(2p)^2}{2m}=k\dfrac{2eq}{r'}$
$\dfrac{4p^2}{2m}=k\dfrac{2eq}{r'}$
$\dfrac{2p^2}{m}=k\dfrac{2eq}{r'}$
$r'=k\dfrac{2eq}{p^2} \times \dfrac{m}{2}$
$=\dfrac{r}{2m}\times \dfrac{m}{2}$
$r'=\dfrac{r}{4}$

Multiple choice physics motion and measurement of distances motion around us motion and rest moving things around us

The height $y$ and horizontal distance $x$ covered by a projectile in a time $t$ seconds are given by the equations $y = 8t - 5t^2$ and $x = 6t$. If $x$ and $y$ are measured in meters, the velocity of projection is:-

  1. $10 \ ms^{-1}$

  2. $6 \ ms^{-1}$

  3. $8 \ ms^{-1}$

  4. $14 \ ms^{-1}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$v _x=\dfrac{dx}{dt}=6$

$v _y=\dfrac{dy}{dt}=8-10t$
$\vec v=v _x\hat{i}+v _y\hat{j}$

$\vec u=\vec v _{t=0}$
$\vec u=6\hat{i}+8\hat{j}$
$u=\sqrt{6^2+8^2}$
$u=10m/s$

Multiple choice physics motion and measurement of distances motion around us motion and rest moving things around us

Estimate the force exerted by a $75 \ W$ bulb on your finger tip (are $1\ cm^{2}$), when is at a distance of $8 \ cm$ from the bulb. (Assume $100\%$ absorption)

  1. $1 \ N$

  2. $3.1 \times 10^{-10} N$

  3. $4 \times 10^{-6} N$

  4. $2 \times 10^{-4} N$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$\begin{array}{l} P=\frac { { \overline { S }  } }{ c } =\frac { { \frac { P }{ { 4\pi { d^{ 2 } } } }  } }{ c } =\frac { { \frac { { 75W } }{ { 4\pi { { \left( { 8.0\times { { 10 }^{ -2 } }m } \right)  }^{ 2 } } } }  } }{ { 3.00\times { { 10 }^{ 8 } }\, m/s } } =3.1\times { 10^{ -6 } }N/{ m^{ 2 } }. \ The\, \, force\, \, is\, \, pressure\, \, times\, \, area, \ we\, \, approximate\, \, the\, \, area\, \, of\, \, a\, \, fingertip\, \, to\, \, be\, \, 1.0\, c{ m^{ 2 } } \ F=PA=\left( { 3.1\times { { 10 }^{ -6 } }N/{ m^{ 2 } } } \right) \left( { 1.0\times { { 10 }^{ -4 } }{ m^{ 2 } } } \right) =3.1\times { 10^{ -10 } }N \end{array}$

Hence,
option $(B)$ is correct answer.

Multiple choice physics motion and measurement of distances motion around us motion and rest moving things around us

A boy of mass $m$ is at one end of a flat boat of mass $M$ and length $l$ which floats stationary on water. If boy moves to the other end,

  1. The boat moves in opposite direction through a distance $d = \dfrac { m l } { ( M + m ) }$

  2. The displacement of boy with respect to ground is $d ^ { 1 } = \dfrac { - M } { ( M + m ) }$

  3. The displacement of boy with reject to ground is $d^{2}=\dfrac{-M}{(M+m)}$

  4. The displacement of boy with reject to ground is$d^{3}=\dfrac{-m}{(m+M)}$
Reveal answer Fill a bubble to check yourself
B Correct answer