Unit 5 Worksheet 1 Answers and Solutions

1.(b)
n+W=ma
n-833N=(85kg)(0m/s/s)
n=833N		2.(b)
n+W=ma
n-833N=(85kg)(+2.0m/s/s)
n=833N+170N
n=1003N
3.(b)
n+W=ma
n-833N=(85kg)(-3.0m/s/s)
n=578N		4.
If the cable breaks the elevator
and the man will accellerate down
at 9.8m/s/s (free fall).
n+W=ma
n-833N=(85kg)(-9.8m/s/s)
n=833N-833M
n=0N
while descending at a
constant speed
n+W=ma
n-666N=(85kg)(0m/s/s)
n=666N		while slowing to a stop
n+W=ma
n-666N=(68kg)(+2.0m/s/s)
n=666N+136N
n=802N

c.
Bathroom scales actually read the normal force, not the force due to gravity.
Therefore the scale would read 666N while descending at a constant
speed (no acceleration) and 802N while slowing to a stop
(up is positive and the acceleration is up).