Motion along a straight line

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1. Mar 14, 2015

Ineedhelp809

1. The problem statement, all variables and given/known data
A bullet fired straight upwards experiences an acceleration due to air resistance of 1m/s2 during its entire flight. If it leaves the barrel of the gun at 300m/s, with what speed does it hit the ground?

2. Relevant equations
None given

3. The attempt at a solution
integral of a=t + c. When c=0, a=t
?
Speed is 300m/s?

2. Mar 15, 2015

Suraj M

I think it will be easier if you do it using the energy concepts.
Equate the change in kinetic energy to the work done by air resistance.
And no it's not 300m/s !
#The change in kinetic energy will include the final velocity term.
Also the mass will get cancelled.

3. Mar 15, 2015

Dick

No, and that's not a very good attempt. What's the total acceleration going up? How high do you get starting with an initial velocity of 300m/s? Then reverse the problem going down.

4. Mar 15, 2015

Dick

It's just kinematics here. The acceleration going up is constant and the acceleration coming down is a different constant. I don't think energy conservation will help all that much.

5. Mar 15, 2015

Ineedhelp809

Do I have to use equations of motion?

6. Mar 15, 2015

Dick

Well, yes. Or integrate them yourself. What's the value of the acceleration going up?

7. Mar 15, 2015

Suraj M

well yes(ignoring our high initial velocity of 300m/s, and assuming g as constant, though there will be a noticeable difference), it still can be done, but yes, it will get a bit more complicated,
for OP: try to split the motion into 2 parts and define the list the physical quantities that you can find out from the given information.