Question

With what speed should a body be thrown upwards so that the distances traversed in 5th second and
6th second are equal ?
(A) 58.4 m/s
(B) 49 m/s
(C) 198 m/s (D) 98 m/s
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Answer 1

(B) is correct

Explanation:

Here, we will use the following equation of motion

s=ut-0.5gt²

take g=9.8m/s²

s at the 5th second is:

s=5u-0.5×9.8×25

s=5u-125.5

s at the 6th second is:

s=6u-0.5×9.8×36

s=6u-176.4

since these displacement are equal:

6u-176.4=5u-125.5

u=176.4-125.5=50.9.

which is approximately 49 m/s