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Determine the stopping distances for an automobile going a constant initial speed. Mastering physics question?

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Determine the stopping distances for an automobile going a constant initial speed of 94 km/h and human reaction time of 0.30 s , for an acceleration a=−3.6m/s^2.

Express your answer using two significant figures.
D= ________ m

Determine the stopping distances for an automobile going a constant initial speed of 94 km/h and human reaction time of 0.30 s, for an acceleration a=−5.8m/s^2.

D=_________ m
asked Aug 29, 2015 in PHYSICS by anonymous

2 Answers

0 votes

(1)

Step 1:

Initial speed of automobile is .

Human reaction time is  sec.

Acceleration is .

.

From Linear motion equations : .

Substitute  and  in the formula.

Find the time, when the automobile stops moving. 

When the automobile is stopped, .

 sec.

Step 2:

Find the distance traveled by the automobile, when  sec.

From Linear motion equation .

Substitute  and  in the formula.

image

image 

Find the distance covered during reaction time. 

image

image.

Find stopping distance by adding results in (1) and (2).

Stopping distance is image.

Solution:

Stopping distance is image.

answered Aug 29, 2015 by cameron Mentor
edited Aug 29, 2015 by cameron
0 votes

(2)

Step 1:

Initial speed of automobile is image.

Human reaction time is  sec.

Acceleration is image.

.

From Linear motion equation : .

Substitute  and image  in the formula.

image

When the automobile is stopped, .

image

image sec.

Step 2:

Find the distance traveled by the automobile, when image sec.

From Linear motion equation : .

Substitute image and image in the formula.

image

image .

Find the distance covered during reaction time. 

image.

Find stopping distance by adding results in (1) and (2).

Stopping distace is image.

Solution:

Stopping distace is image.

answered Aug 29, 2015 by cameron Mentor

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