Answer
$$deceleration = 1.67 \space m/s^2$$
Work Step by Step
Using equation 12-4:
$$v = v_0 + a_ct$$
1. Solve for the acceleration and substitute the values:
$$v - v_0 = a_ct$$ $$a_c = \frac{v - v_0}{t} = \frac{10 -35}{15} = -1.67 \space m/s^2 $$
2. The deceleration is equal to the negative of the acceleration:
$$deleceration = -(-1.67 \space m/s^2) = 1.67 \space m/s^2$$
