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# An object travels 10 km at a speed of 100 m/s and another 10 km at 50 m/s. The average speed over the whole distance is:A.75m/sB.55m/sC.66.7m/sD.33.3m/s

Last updated date: 20th Jun 2024
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Hint: In this question we will use the basic expression of average speed to find the result. First we will calculate the total time and total distance travelled by the object and then by substituting these values in the average speed expression will give us the answer. Further we will discuss the basics of speed.
Formula used:
${s_{avg}} = \dfrac{d}{t}$

Here, as we already know, the average speed is given by the ratio of total distance traveled by the object and the total time taken by the object to travel that particular distance.
We first calculate the time for first 10km will be given by:
${t_1} = \dfrac{{10 \times {{10}^3}}}{{100}} = 100\sec$
Now, the time for the last 10km will be given as:
${t_2} = \dfrac{{10 \times {{10}^3}}}{{50}} = 200\sec$
From above results, we calculate the total time as:
$100 + 200 = 300\sec$
Now, we know that the total distance is given as:
$10 + 10 = 20km$
At last, we use the above values to find the average speed of the object, which is given by:
\eqalign{& {s_{avg}} = \dfrac{{20000}}{{300}} \cr & \therefore {s_{avg}} = 66.7m/\operatorname{s} \cr}

Therefore, the correct option is C) i.e., the average speed of the object is 66.7m/s.