A car is initially traveling west at 25 mph,and makes a turn north.As the car finishes the turn,its velocity is 20 mph north.It takes 3.5 seconds to complete the turn.What is the average acceleration of the car while it is turning,in mph/s? Let east be the positive-x direction and north be the positive-y direction.
A)-7.1 + 5.7
B)7.1 - 5.7
C)5.7 - 7.1
D)-5.7 + 7.1

Question

A car is initially traveling west at 25 mph,and makes a turn north.As the car finishes the turn,its velocity is 20 mph north.It takes 3.5 seconds to complete the turn.What is the average acceleration of the car while it is turning,in mph/s?​ Let east be the positive-x direction and north be the positive-y direction.
A)​-7.1 + 5.7 
B)​7.1 - 5.7 
C)​5.7 - 7.1 
D)​-5.7 + 7.1

Quizplus · Accepted Answer

We can use the formula for average acceleration:

average acceleration = (final velocity - initial velocity) / time

Since the car initially traveled west (negative x direction) and then turned north (positive y direction), we can break up the velocity vectors into their x and y components:

initial velocity = -25 mph in the x direction
final velocity = 20 mph in the y direction

Now we can plug in the values:

average acceleration = ((0 mph, 20 mph) - (-25 mph, 0 mph)) / 3.5 s

Simplifying the vector subtraction:

average acceleration = (25 mph, 20 mph) / 3.5 s

Finally, dividing each component by 3.5 s:

average acceleration = (7.1 mph/s, 5.7 mph/s)

Therefore, the correct answer is A, as it lists these values with the correct signs.

A Car Is Initially Traveling West at 25 Mph,and Makes