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The average speed of a nitrogen molecule in air is about 670 m/s, and its mass is about (4.68 x 10^-26)kg.

(a) If it takes (3.60 x 10^-13)s for a nitrogen molecule to hit a wall and rebound with the same speed but moving in an opposite direction (assumed to be the negative direction), what is the average acceleration of the molecule during this time interval?

____________ m/s^2

(b) What average force does the molecule exert on the wall?

____________N

2. Homework Equations

Ok, here is the basic kinematic equation and force equation. I used both of these equations to talk to my professor after class 2 days ago to solve it and he got the same answer. I emailed him today and he said you use the average acceleration kinematic equation to solve it but thats what we did, i dont know if he doesnt remember or there is some secret one that i have never been informed of.

a)- (final velocity - initial velocity) / (change in time) = average acceleration

b)- (mass * average acceleration) / (change in time) = average force

3. The Attempt at a Solution

a) (-670-670) / (3.6 x 10^-13) = approximately (-3.722 x 10^15)m/s^2

Webassign's response: "Answer has wrong sign"

My next answer: ([positive now]3.722 x 10^15)m/s^2

Webassign's response: "Answer has wrong sign"

Advice on tricky wording or problem or something?

b) [(3.722 x 10^15)*(4.68 x 10^-26)] / (3.6 x 10^-13) = 483.86 N

Webassign's response: "Answer is off by an order of magnitude"

My next answer: -483.86 N

Webassign's response: "Answer has the wrong sign"

Honestly this makes no sense but if anyone can help or gets a different answer you help would be greatly appreciated