Question

Sarah is running a race and is almost to the finish line. In the last 5 seconds, her velocity changes from 2m/s to 4m/s. What is her average acceleration during the last 5 seconds of the race?

Answer 1

Answer:

$\boxed {\boxed {\sf a= \frac {2}{5} \ or \ 0.4 \ m/s^2}}$

Explanation:

Acceleration is found by dividing the change in velocity by the time. The formula is:

$a= \frac {v_f-v_i}{t}$

where $v_f$ is the final velocity, $v_i$ is the initial or starting velocity, and $t$ is the time.

Her velocity changes from 2 meters per second to 4 meters per second in the 5 seconds. Therefore:

$v_f= 4 \ m/s \\v_i= 2 \ m/s \\t=5 \ s$

Substitute the values into the formula.

$a= \frac { 4 \ m/s- 2 \ m/s}{5 \ s}$

Solve the numerator and subtract.

$a= \frac { 2 \ m/s}{5 \ s}$

Divide.

$a= \frac{2}{5} \ m/s/s= \frac{2}{5} \ m/s^2$

This can also be written as a decimal.

$a=0.4 \ m/s^2$

Her average acceleration during the last 5 seconds of the race is 2/5 or 0.4 meters per square second.

Answer 2

Answer:

Solution :-

Here

Initial velocity = 2 m/s

Final velocity = 4 m/s

Time = 5 sec

v = u + at

4 = 2 + a(5)

4 - 2 = a(5)

2 = 5a

2/5 = a

Hence, acceleration is 2/5 m/s²