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CP CALC You are standing on a bathroom scale in an
Chapter 8, Problem 77P(choose chapter or problem)
CP CALC ?You are standing on a bathroom scale in an elevator in a tall building. Your mass is 64 kg. The elevator starts from rest and travels upward with a speed that varies with time according to v(t) = (3.0 m/s2)t + (0.20 m/s3)t2. When t = 4.0 s, what is the reading on the bathroom scale?
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QUESTION:
CP CALC ?You are standing on a bathroom scale in an elevator in a tall building. Your mass is 64 kg. The elevator starts from rest and travels upward with a speed that varies with time according to v(t) = (3.0 m/s2)t + (0.20 m/s3)t2. When t = 4.0 s, what is the reading on the bathroom scale?
ANSWER:Solution 77P Step 1: Your mass is 64 kg. The elevator starts accelerating upwards. The velocity as a function of time is given as, 2 v(t) = 3t + 0.20 t ----------------(1) As we know that, acceleration is the time derivative of velocity, so let’s find it. dv d 2 a = dt = dt(3t + 0.20 t ) = 3 + (0.20 × 2) t = 3 + 0.40t St time t = 4 s, the acceleration will be, a = 3 + 0.40 × 4 = 4.6 m/s .2