This is the boss. No calculator: the position function is a cubic with small whole-number coefficients, the moment $t_0$ is 1, 2 or 3, and every number fits in your head. One function, one long inspection, and every answer feeds the next: name the rule that gives velocity from position, find the position at $t_0$, differentiate for the velocity there, name the rule that gives acceleration, find it, then write the tangent line to the position graph at $t_0$ from the two numbers you already hold and read off where it says the cart would be one second later.

Everything in the chapter rides in here: the power rule term by term with the constant dropped, the derivative as a rate in m/s and m/s², the tangent line as $s(t_0) + v(t_0)(t - t_0)$ with the slope a NUMBER, and the line as a prediction that is not the curve. Write each line down as you go; a slip in line two walks all the way to line seven. 5★ under par is the chapter crown.