Physics 12 energy, work question

AI Thread Summary
The discussion revolves around calculating the time it took for a bullet to stop after penetrating a sandbag and the average force acting on it. The initial calculations provided an incorrect force value of 18490 N, prompting clarification on its derivation. Participants suggest using kinematic equations to determine acceleration based on the bullet's initial and final velocities, as well as the distance penetrated. This approach allows for accurate calculations of both the time taken to stop and the average force exerted on the bullet. The focus remains on applying proper physics principles to solve the problem effectively.
gdhillon
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Q:A sandbag stops a 12 g bullet which was traveling at 860 m/s. The bullet penetrated a
distance of 24 cm into the sand?
a) How long did it take the bullet to stop?
b) What average force acted on the bullet?
first i used ∇p=Ft so 10.32=18490t t=5.6*10^-4 sec
then i put that into e=1/2mv^2 (to get letter A) so 1/2(.012)860^2= 4437.6
 
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gdhillon said:
first i used ∇p=Ft so 10.32=18490t
Where did the 18490 come from? The data tells you neither F nor t, only distance.
 
You know the distance traveled by the bullet, it's initial velocity, and it's final velocity. Use a kinematics equation which relates them to find out the acceleration of the bullet. Now use that to find the time it travels for using another kinematics equation. And then use that to calculate the average force using the formula you wrote.
 

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