A three-wheeler starts from rest, accelerates uniformly with $1\; m/s^{2}$ on a straight road for $10\; s$, and then moves with uniform velocity. Plot the distance covered by the vehicle during the $n ^{\text {th }}$ second $( n =1,2,3 \ldots .)$ versus $n$. What do you expect this plot to be during accelerated motion : a straight line or a parabola?
Straight line
Distance covered by a body in $n^{\text {th }}$ second is given by the relation $D_{n}=u+\frac{a}{2}(2 n-1)\ldots(i)$
Where,
$u=$ Initial velocity
$a=$ Acceleration
$n=$ Time $=1,2,3, \ldots \ldots, n$
In the given case, $u=0$ and $a=1 m / s ^{2}$
$\therefore D_{n}=\frac{1}{2}(2 n-1)\dots (ii)$
This relation shows that
$D_{n} \propto n \ldots (iii)$
Now, substituting different values of $n$ in equation (iii), we get the following table
$n$ | $1$ | $2$ | $3$ | $4$ | $5$ | $6$ | $7$ | $8$ | $9$ | $10$ |
$D_n$ | $0.5$ | $1.5$ | $2.5$ | $3.5$ | $4.5$ | $5.5$ | $6.5$ | $7.5$ | $8.5$ | $9.5$ |
The plot between $n$ and $D_{n}$ will be a straight line as shown
since the given three-wheeler acquires uniform velocity after 10 s, the line will be parallel to the time-axis after $n=10 s$
Draw the $x\to t$ graphs for positive, negative and zero acceleration.
If the velocity of a particle is given by $v = {(180 - 16x)^{1/2}} m/s$, then its acceleration will be.......$ms^{-2}$
An object with a mass $10 \,kg$ moves at a constant velocity of $10 \,m/sec$. A constant force then acts for $4\, second$ on the object and gives it a speed of $2\, m/sec$ in opposite direction. The acceleration produced in it, is ........ $m/{\sec ^2}$
A monkey climbs up a slippery pole for $3$ and subsequently slips for $3$. Its velocity at time $t$ is given by $v (t) = 2t \,(3s -t)$ ; $0 < t < 3$ and $v(t) =\,-\, (t -3)\,(6 -t)$ ; $3 < t < 6$ $s$ in $m/s$. It repeats this cycle till it reaches the height of $20\, m$.
$(a)$ At what time is its velocity maximum ?
$(b)$ At what time is its average velocity maximum ?
$(c)$ At what time is its acceleration maximum in magnitude ?
$(d)$ How many cycles (counting fractions) are required to reach the top ?
What would be the stopping distance if the velocity of vehicle becomes three times ?