Physics

Problem

A car is travelling at

5\,\text{m/s}

when the driver presses the accelerator. The car then: • Accelerates uniformly at

2\,\text{m/s}^2

for

5\,\text{s}

. • Immediately afterwards, decelerates uniformly at

1\,\text{m/s}^2

for

8\,\text{s}

. Answer the following questions, using clear and systematic calculations: (i) What is the velocity of the car at the end of the first

5\,\text{s}

? (ii) What is its velocity at the end of the next

8\,\text{s}

(the end of the whole

13\,\text{s}

)? (iii) Determine the average acceleration of the car for the complete

13\,\text{s}

interval. (iv) Calculate the total displacement of the car during the

13\,\text{s}

. (v) Compare the magnitude of the average acceleration obtained in part (iii) with the accelerations in each phase and give a reason for the observed value. a. What is the velocity of the car at the end of the first

5\,\text{s}

? b. What is its velocity at the end of the next

8\,\text{s}

(the end of the whole

13\,\text{s}

)? c. Determine the average acceleration of the car for the complete

13\,\text{s}

interval. d. Calculate the total displacement of the car during the

13\,\text{s}

. e. Compare the magnitude of the average acceleration obtained in part (iii) with the accelerations in each phase and give a reason for the observed value.

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