The position vector of a particle is given by →r=1.2t^i+0.9t2^j−0.6(t3−1)^k where t is the time in seconds from the start of motion and where →r is expressed in metres.
Determine the power (P=→F.→v) in watts produced by
the force →F=(60^i−25^j−40^k)N which is acting on the particle at time t=4 seconds.
→v=d→rdt=1.2^i+1.8t^j−1.8t2^k
At t=4s,→v=1.2^i+7.2^j−28.8^k
P=→F.→v=(60^i−25^j−40^k)⋅(1.2^i+7.2^j−28.8^k)
=1044W