Final answer:
To find the initial velocity of an object thrown straight up and caught after 8 seconds, we use the equation for uniformly accelerated motion with gravity's acceleration. The object takes 4 seconds to reach the peak, and the initial velocity is found to be 39.24 m/s.
Step-by-step explanation:
Calculating the Initial Velocity of the Thrown Object
To calculate the initial velocity of an object thrown straight up into the air and caught after 8 seconds, we can use the equations of motion for uniformly accelerated motion. The acceleration due to gravity, which is approximately 9.81 m/s2, will cause the object to decelerate on its way up, stop momentarily at the peak of its trajectory, and then accelerate back downwards.
The total time of 8 seconds includes both the ascent and the descent of the object. Therefore, the time it takes to reach the peak is half of 8 seconds, which is 4 seconds.
Using the equation v = u + at, where v is the final velocity (0 m/s at the peak), u is the initial velocity which we are trying to find, a is the acceleration due to gravity (-9.81 m/s2 when considering upward movement as positive and downward as negative), and t is the time, we can rearrange the equation to solve for u:
u = v - at
Plugging in the values, we get:
u = 0 - (-9.81 m/s2)(4 s)
Therefore, the initial velocity u is 39.24 m/s.
This is the speed at which the object must have been thrown upward.