Please start with 1 or more of the following equations: 1. d=.5(Vf+Vi)*t 2. Vf=V
ID: 1340116 • Letter: P
Question
Please start with 1 or more of the following equations:
1.
d=.5(Vf+Vi)*t
2.
Vf=Vi+at
3.
d=Vi(t)+.5at^2
4.
d=Vf(t)-.5at^2
5.
Vf^2=Vi^2+2ad
Since there is generally more than one way to solve these problems, please state which of the 5 kinematic equations you are using to solve this problem as well as briefly define variables and your thought process (e.g. "First I solved for V_1 of x component, then I solved for delta x..." etc. etc.). Thank you!
Jake stands in an elevator. As the elevator speeds up departing the 1st floor, and then slowing down approaching 11th floor, Jake feels his weight first increasing, then decreasing. The magnitude of the acceleration of the elevator is the same 2.1 m/s2 in both cases (but the direction is different). If Jake feels 495.6 N heavier when he is departing the 1st floor, than when he is approaching the 11th floor, then what is his true weight?
Explanation / Answer
As the elevator speeds up departing the 1st floor and then slowing down approaching 11th floor.
Jake feels his weight first increasing then decreasing.
magnitude of acceleration in both cases, a = 2.1 m/s2
When he is departing the 1st floor, then Jake feels, F = 495.6 N
mass of the elevator in first case, m = F / a { eq.1 }
inserting the values in above eq.
m = (495.6 N) / (2.1 m/s2)
m = 236 kg
When he is approaching the 11th floor, then his true weight will be given as :
using an eq. T - mg = ma
T = m (g + a) { eq.2 }
where, g = acceleration due to gravity = 9.8 m/s2
inserting the values in eq.2,
T = (236 kg) [(9.8 m/s2) + (2.1 m/s2)]
T = (236 kg) (11.9 m/s2)
T = 2808.4 N