Physics Regent Exam, June 19, 2018
3. While taking off from an aircraft carrier, a jet starting from rest accelerates uniformly to a final speed of 40. meters per second on a runway that is 70. meters long. What is the magnitude of the acceleration of the jet?
Let's first determine what we are given. We have initial speed = 0 since the jet starts at rest. We also have a final speed of 40 m/s. We have distance of 70 meters, and we are asked to find the magnitude of acceleration. Looking at the referent table formulas on the last page, we need to find a formula that has what we are given. The formula is
vf^2= vi^2 + 2ad
Let's plug in the answers to find a
40^2= 0 + 2a*70
a=11.43 m/s^2, leaving us with choice 4 as the correct answer.
7. A ball is rolling horizontally at 3.00 meters per second as it leaves the edge of a tabletop 0.750 meter above the floor. The ball lands on the floor 0.391 second after leaving the tabletop. What is the magnitude of the ball’s acceleration 0.200 second after it leaves the tabletop? [Neglect friction.]
Let's put together all the variables we are given.
Initial velocity = 3m/s
time total = 0.381 s
final velocity = 0m/s since the ball lands
Now, lets think about this problem. The ball, here, drops from above the ground. Therefore it is accelerating due to the force of gravity. What is the acceleration due to gravity? 9.81 m/s2 This is always the acceleration due to gravity.
Therefore, this is the correct answer we would choose for this problem.
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