Final answer:
The average acceleration of the car is calculated by using the formula a = Δv / Δt. Converting 70 km/hr to 19.44 m/s and dividing by the time interval of 7 seconds gives 2.77 m/s², which is then converted back to km/hr² to be 35.97 km/hr², suggesting an error in the question's options.
Step-by-step explanation:
The question is asking to find the average acceleration of a car that can accelerate from rest to 70 km/hr in 7 seconds. Acceleration is the rate of change of velocity with time. Since acceleration is constant, we can use the formula a = Δv / Δt, where a is acceleration, Δv is the change in velocity, and Δt is the change in time.
First, we convert the final velocity from km/hr to m/s: 70 km/hr ÷ 3.6 = 19.44 m/s. Then, since the car starts from rest, the initial velocity vi is 0. The change in velocity Δv is 19.44 m/s - 0 m/s = 19.44 m/s. The change in time Δt is 7 seconds.
Using the formula: a = Δv / Δt = 19.44 m/s ÷ 7 s = 2.77 m/s². To convert this back to km/hr², multiply by 3.6² (since 1 m/s = 3.6 km/hr). This gives us an acceleration of 2.77 m/s² × (3.6²) = 35.97 km/hr² which is not listed in the options provided, indicating a possible error in the question or the answer choices.