Final answer:
The acceleration of a car that goes from a standstill to 81 m/s in 9.0 seconds is calculated using the formula (v - u) / t. The answer is 9.0 m/s^2. Therefore, the correct answer is b) 9.0 m/s².
Step-by-step explanation:
The student has asked about a physics problem involving linear acceleration. To determine the acceleration of the car, we use the formula for acceleration ∑a = (v - u) / t, where v is the final velocity, u is the initial velocity, and t is the time. As the car accelerates from a standstill (which means its initial velocity u is 0 m/s) to 81 m/s in 9.0 seconds, we can calculate the acceleration as follows:
Acceleration (a) = (v - u) / t
= (81 m/s - 0 m/s) / 9.0 s
= 81 m/s / 9.0 s
= 9.0 m/s²
Therefore, the correct answer is b) 9.0 m/s².