A bullet of mass 12g strikes a solid surface at a speed of 300 m s^ -1. The bullet penetrates to a depth of 3.0 cm.
(i) Calculate the average force resisting the motion of the bullet in the solid.
The solution:
F = ma
= 0.012 * (-1.5) * 10^6
= -18 000 N
Average resistive force is 18 000 N
Why is it that the force is positive? Why can't we just leave it as negative? Why must we must change it to positive?
2007-10-29 17:59:29 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
The force is negative with respect to force of the bullet. But it is positive with respect to the resistance to the bullet which is what you were ask to calculate.
2007-10-29 18:21:26 · answer #1 · answered by Mr. Un-couth 7 · 0⤊ 0⤋
my guess would be that the answer must be positive to show how much force was used against the bullet, if left negative then it could mean that there was a force, such as propulsion to help the bullet go faster. just a guess.: )
2007-10-30 01:07:09 · answer #2 · answered by Anonymous · 0⤊ 0⤋
I'm not so sure but I think F in your solution is referring to the reaction force.
Forces always come in pairs, right?
2007-10-30 03:44:18 · answer #3 · answered by Anonymous · 0⤊ 0⤋