A car starts from rest and moves along x- axis with constant acceleration 5, ms^{-2} for 8,sec . If

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7. MOTION

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A car starts from rest and moves along the $x-$ axis with constant acceleration $5\, ms^{-2}$ for $8\,\sec $. If it then continues with constant velocity, what distance will the car cover in $12\,\sec $ since it started from the rest ?

Option A

Option B

Option C

Option D

Solution

The distance travelled in first $8 \,s ,\,\, x_{1}=0+\frac{1}{2}(5)(8)^{2}=160\, m$

At this point the velocity $v=u+a t=0+(5 \times 8)=40 \,m s^{-1}$

Therefore, the distance covered in last four seconds, $x _{2}=(40 \times 4)\, m =160\, m$

Thus, the total distance $x=x_{1}+x_{2}=(160+160) \,m =320\, m$

Standard 9

Science

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