Midterm Exam Unit

4 Comments

Christopher Crocker • 4 years, 9 months agologin to reply

#17 on the MC Midterm review. We believe it to be 16 times greater not 8.

Rosanna Satterfield • 4 years, 6 months agologin to reply

Yes, you are correct, number 17 is 16 times greater, thank you! The answer key has been revised.

Heather Vinick • 2 years, 6 months agologin to reply

Can someone please explain how to find the answer to #15, 17, and 20 on the midterm multiple choice review. Thank you.

John Ennis • 2 years, 6 months agologin to reply

Heather, here you go: #15. Use the Second Kinematics Equation. Initial velocity is zero. so the equation becomes Delta y = 1/2at^2. Solve this for t and you find that t is proportional to the square root of delta y. So the package that is dropped from a height of 4H takes 2 times as much time to hit the ground as the package at height h. Answer B. #17. Use the Third Kinematics Equation (there is no time in the problem). The final velocity at the max height is zero, so the equation, solved for delta y is: delta y = (v initial)^2/2a. The max height depends on the square of the initial velocity - so the arrow fired at 4 times the initial velocity of the other one rises to a height 16 times that one. Answer D. #20. Use the second kinematics equation with the initial velocity and position equal to zero. Solve it for a. a = 2x/t^2. Plug in the position and time at any of the points and you get a = 4 m/s^2. If you take the last point where x = 50 and t = 5 you get: a = 2(50)/5^2 = 4. Answer C.

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