Because many objects in space don't radiate any optical (visible) radiation at all.
And other objects, like stars, radiate a lot of invisible radiation in addition to the
visible light from them. So the ability to detect and measure invisible radiation
makes it possible to learn a lot more about objects in space than we could if
we could only use their visible light.
Answer:
time=4, answer choice A
time=5.5, answer choice B
Explanation:
This is taken from the kinematic equation, v=vo+(1/2)at^2
Velocity at time 4 = 30+(2.5)(4)^2
Velocity at time 5.5 = 30+(2.5)(5.5)^2
Velocity at time 4 seconds = 70 m/s
Velocity at time 5.5 seconds = 105.63 m/s