$A$ particle moves along a straight line such that its displacement $x$ varies with time $t$ as $x = \alpha t^3 + \beta t^2 + \gamma$,where $\alpha, \beta, \gamma$ are constants. $V_1$ is the average velocity of the particle during its journey between $t = 1 \ s$ and $t = 3 \ s$. $V_2$ is the instantaneous velocity of the particle at $t = 3 \ s$. The ratio $\frac{V_1}{V_2}$ is

  • A
    $\frac{27 \alpha + 9 \beta}{26 \alpha + 6 \beta}$
  • B
    $\frac{9 \alpha + 3 \beta}{18 \alpha + 4 \beta}$
  • C
    $\frac{13 \alpha + 5 \beta}{27 \alpha + 6 \beta}$
  • D
    $\frac{26 \alpha + 8 \beta}{9 \alpha + 3 \beta}$

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At time $t=0$,a car moving along a straight line has a velocity of $16 \; m/s$. It slows down with an acceleration of $a = -0.5t \; m/s^2$,where $t$ is in seconds. Mark the correct statement$(s)$.

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Statement $(I)$: An object subjected to velocities $\overrightarrow{v_1}$ and $\overrightarrow{v_2}$ has a resultant velocity with magnitude $|\vec{v}| = |\overrightarrow{v_1}| + |\overrightarrow{v_2}|$.
Statement $(II)$: The magnitude of displacement is either less than or equal to the path length of an object between two points.
Statement $(III)$: The instantaneous acceleration is the limiting value of the average acceleration as the time interval approaches zero.
Which of the following is correct?

$A$ person of height $1.6 \ m$ is walking away from a lamp post of height $4 \ m$ along a straight path on the flat ground. The lamp post and the person are always perpendicular to the ground. If the speed of the person is $60 \ cm \ s^{-1}$,the speed of the tip of the person's shadow on the ground with respect to the person is . . . $cm \ s^{-1}$.

In the $s-t$ equation $(s=10+20t-5t^2)$,match the following columns.
Column $I$ Column $II$
$(A)$ Distance travelled in $3\,s$ $(p)$ $-20$ units
$(B)$ Displacement in $1\,s$ $(q)$ $15$ units
$(C)$ Initial acceleration $(r)$ $25$ units
$(D)$ Velocity at $4\,s$ $(s)$ $-10$ units

$A$ passenger arriving in a new town wishes to go from the station to a hotel located $10 \;km$ away on a straight road from the station. $A$ dishonest cabman takes him along a circuitous path $23 \;km$ long and reaches the hotel in $28 \;min$. What is
$(a)$ the average speed of the taxi,
$(b)$ the magnitude of average velocity? Are the two equal?

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