A stone is projected vertically up from the ground with velocity 40ms^(-1). The interval of time between the two instants at which the stone is at a height of 60m above the ground is (g=10ms^(-2))

A stone is projected vertically up from the ground with velocity 40ms^

1.	A stone is projected vertically up from the ground with velocity 40ms^(-1). The interval of time between the two instants at which the stone is at a height of 60m above the ground is (g=10ms^(-2))
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