Refer to the graph in figure. Match the following
Graph | Characteristics |
$(A)$ | $(i)$ has $v > 0$ and $a < 0$ throughout |
$(B)$ | $(ii)$ has $x > 0,$ throughout and has a point with $v = 0$ and a point with $a = 0$ |
$(C)$ | $(iii)$ has a point with zero displacement for $t > 0$ |
$(D)$ | $(iv)$ has $v < 0$ and $a > 0$ |
We have to analyse slope of each curve i.e., $\frac{d x}{d t}$ For peak points $\frac{d x}{d t}$ will be zero as $x$ is maximum at peak points.
For graph $(a)$, there is a point $(B)$ for which displacement is zero. So, a matches with $(iii)$
In graph (b), $x$ is positive $(>0)$ throughout and has a point $\mathrm{B}_{1}$ with $\mathrm{V}=\frac{d x}{d t}=0$. As at point of curvature changes $a=0$, So $b$ matches with $(ii)$
In graph $(c)$, slope $\mathrm{V}=\frac{d x}{d t}$ is negative hence, velocity will be negative. So, it matches with (iv)
In graph $(d)$, as slope $\mathrm{V}=\frac{d x}{d t}$ is positive hence, $\mathrm{V}>0$
Hence, $d$ matches with $(i)$
A particle starts from origin at $t=0$ with a velocity $5 \hat{i} \mathrm{~m} / \mathrm{s}$ and moves in $x-y$ plane under action of a force which produces a constant acceleration of $(3 \hat{i}+2 \hat{j}) \mathrm{m} / \mathrm{s}^2$. If the $x$-coordinate of the particle at that instant is $84 \mathrm{~m}$, then the speed of the particle at this time is $\sqrt{\alpha} \mathrm{m} / \mathrm{s}$. The value of $\alpha$ is___________.
What will be change in speed of moving object if both speed and acceleration are positive or negative ?
Read each statement below carefully and state with reasons and examples, if it is true or false
A particle in one-dimensional motion
$(a)$ with zero speed at an instant may have non-zero acceleration at that instant
$(b)$ with zero speed may have non-zero velocity.
$(c)$ with constant speed must have zero acceleration.
$(d)$ with positive value of acceleration must be speeding up.
A particle moves for $8\, seconds$. It first accelerates from rest and then retards to rest. If the retardation be $3\, times$ the acceleration, then time for which it accelerates will be