SOLUTION: The position of a 140kg body is given by S = 3t^2 - 7t + 4. Where S is in meters and t is in seconds. Find the velocity of the body when s = 70.

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Question 1082909: The position of a 140kg body is given by S = 3t^2 - 7t + 4. Where S is in meters and t is in seconds. Find the velocity of the body when s = 70.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
First find t when S=70.
3t%5E2-7t%2B4=70
3t%5E2-7t-66=0
%28t-6%29%283t-11%29=0
Only positive t allowed here.
t-6=0
t=6s
.
.
To find the velocity, take the derivative of S.
dS%2Fdt=6t-7
So when t=6,
v=dS%2Fdt=6%286%29-7
v=36-7
v=29m%2Fs