CBSE Class 9 Answered
A car starts from the rest and accelerates at the rate of 5m/s2. It continue accelerating for 10 s and then move at constant velocity for next 10 s. Calculate the total distance traveled by the car in 20s. (5)
Asked by siddsag2972 | 11 May, 2020, 12:48: PM
a = 5 m/s2
u =0
v =?
Distance covered by car when it was still accelerating in for 10 s is given by 2nd equation of motion,
s = ut + 1/2 at2
![s subscript 1 space equals u t subscript 1 space plus space 1 half a t subscript 1 superscript 2 space
equals space 0 space plus space 1 half cross times left parenthesis 5 right parenthesis space open parentheses 10 close parentheses squared space
s subscript 1 equals space 250 space m space](https://images.topperlearning.com/topper/tinymce/cache/28eafe52db68d22997e172211bb324ce.png)
Now, it attains a constant speed. This constant speed can be calculated using first equation of motion,
v = u + at
v = 0 + (5) x (10)
v = 50 m/s
Now, let's calculate the distance travelled in next 10 s.
As the velocity attains the constant velocity, the acceleration will become zero.
Hence,
![s subscript 2 space equals u t subscript 2 space plus space 1 half a t subscript 2 superscript 2 space
equals space 50 space cross times space left parenthesis 10 right parenthesis space plus space 1 half cross times left parenthesis 0 right parenthesis space open parentheses 10 close parentheses squared space
s subscript 2 equals space 500 space m space](https://images.topperlearning.com/topper/tinymce/cache/9e73be3fc584e84283f1ee3c7ca81d1c.png)
Thus, the total distance covered in these 20 s = s1 + s2 = 250 + 500 = 750 m
Answered by Shiwani Sawant | 11 May, 2020, 16:10: PM
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