A particles with mass 3.7 kg moves in the x direction according to the following function: x(t)=−7+4t+3t2−4t3. (the units of each coefficient are meters, and time is measured in seconds). At time t=7.8, what is the net force acting on the particle?
since a = x" = 6-24t
a(7.8) = -181.2
F = ma = -670.4 N