Please answer theses questions with explanations. I’m not sure about my answers

Question

Please answer theses questions with explanations. I’m not sure about my answers not this paper.

PHYS 211-Fall 2017 Midterm 1 Form B go You throw a ball vertically upwards with an initial speed V and it takes a time T for return to your hands (catching it at the same height i was released). You would like to throw the same ball upwards again but this time have it spend twice the time in the air (2T), You then should throw the ball upwards with a speed of 4e A. V2 2T B. 2V D. 4V 1-2t o4h t- 2 E, Not enough information is provided A particle moves in one dimension according the equation z=-2t2 +4t + 6 where x is measured in meters and t is measured in seconds. What is the particle's 11. acceleration at t =0 s? -, u4 A. 4 m/s2 -4 m/s2 C. -6 ms2 D. 0 m/s2 E. 6 m/s2 4

Explanation / Answer

10 .

Time taken by ball is given by.

Time, T = 2*V/g

If time is 2T.

T2 = 2*T

(2*velocity)/g = 2*T

(2*velocity)/g = 2*2*V/g

so new velocity will be.

Velocity = 2V

Hence option (B) is correct.

11-

x = -2t^2 + 4t +6

Double differential gives.

dx^2/dt^2 = -4

Acceleration ,

a = -4 m/s^2

Option (B) is correct.

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