Final answer:
The velocity and speed of the particle when t=4 are both 35 m/s since the derivative of the position function s=f(t)=12+35t+1 with respect to time is constant at 35 m/s.
Step-by-step explanation:
The equation of motion for the particle given is s = f(t) = 12 + 35t + 1. To find the velocity at a particular time t, we need to take the derivative of the position function with respect to time to get v(t). For our function, we take the derivative and get:
v(t) = d(12 + 35t + 1)/dt = 35 m/s.
The speed is the absolute value of the velocity and since velocity is constant and positive, speed and velocity are the same at t = 4 s, thus the speed is also 35 m/s.
To summarize, the velocity and speed of the particle when t = 4 are both 35 m/s.