An object's two dimensional velocity is given by v(t) = ( 3t^2 - 5t , t )v(t)=(3t25t,t). What is the object's rate and direction of acceleration at t=2 t=2?

1 Answer
Jul 3, 2016

veca(t)=(7hati+hatj)m/s^2a(t)=(7ˆi+ˆj)ms2

Explanation:

I'm guessing they're using normal convention replaced by brackets.

So, in vectorial form, vec{v(t)}=(3t^2-5t)hati+thatjv(t)=(3t25t)ˆi+tˆj

Acceleration is the time derivative of velocity, so you go that.
veca=d/dt(vecv(t))=d/dt(3t^2-5t)hati+d/dt(t)\hatja=ddt(v(t))=ddt(3t25t)ˆi+ddt(t)ˆj

I'm sure you know differentiation, hence we'll get acceleration
veca(t)=(6t-5)hati+1hatja(t)=(6t5)ˆi+1ˆj

We need to find acceleration at time t=2t=2, substitute,
veca(t)_{t=2}=(6*2-5)hati+hatja(t)t=2=(625)ˆi+ˆj

In the end, you'll get why the answer is as given in the box.