- #1
jiayingsim123
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Homework Statement
A car of mass 1200kg is at rest on a level road. Two people push it, producing a total force given by (240-12t) Newtons, where t is the time in seconds, until this becomes zero after 20 seconds. How fast is the car then moving, and how far does it move while it is being pushed.
The Attempt at a Solution
I got the answer for the first part of the question, which asks how fast the car is then moving, but I can't get the answer for the second part of the question. I got 80/3m instead of 8/3m as stated in the book. Here is my attempt at the question.
m=1200kg
F=(240-12t)N
F=ma
a=F/m=0.2-0.01t
v=∫0.2-0.01tdt (with upper limit=20 and lower limit 0)
= [0.2t-(0.01t^2)/2] (with upper limit=20 and lower limit=0)
= 4-2
= 2 (this is the correct answer)
s = ∫0.2t-(0.01t^2)/2dt (with upper limit=20 and lower limit=0)
= 80/3m
Please include detailed explanations along with your solution, thanks! :D