TBR Momentum and Torque psg 1 #4

[zoner]

Wondering if anyone can help me with the collision graph.

On Page 192 question 4 in passage 1 there is a question about find the best representative graph for relationship between the bullet mass and the final speed of the block after the collision. Its related to a passage given.

I understand theoretically why the answer should be A, but not in terms of equation. The conversation of momentum equation is linear no? then why is the line curved? I understand that choice A is not either inverse or exponential. What kind of curve is that?

Any help would be greately appreicated.

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[BerkReviewTeach]

Wondering if anyone can help me with the collision graph.

On Page 192 question 4 in passage 1 there is a question about find the best representative graph for relationship between the bullet mass and the final speed of the block after the collision. Its related to a passage given.

I understand theoretically why the answer should be A, but not in terms of equation. The conversation of momentum equation is linear no? then why is the line curved? I understand that choice A is not either inverse or exponential. What kind of curve is that?

Any help would be greately appreicated.

The key thing on this question is to recognize that the bullet's speed is fixed at 200 m/s. It collides with a stationary block of a fixed mass, so final total mass is greater than the initial mass, so the final speed must be less than the initial speed.

If the mass of the bullet increases, while the speed is fixed at 200 m/s, then the bullet has greater and greater initial momentum (pinitial = mbullet(200)). After it collides with the block, the post-collision momentum of the bullet/block system (pfinal = (mbullet + mblock)vfinal must be greater as well (because it equals the initial momentum). This means that the graph should show an increasing trend, which eliminates choice C.

The combined mass of the bullet and block will always be greater than the mass of the bullet, so the final speed can get close to, but never equal 200 m/s. Choice D shows speed going up to infinity, so it's out. Choice B also shows the final speed increasing to infinity, which eliminates it. If the bullet were so small in mass compared to the box that the mass of the box essentially didn't change, then the final speed would barely be above zero, which also negates choice B.

 

[zoner]

BRT, I was just wondering, is this your full time job? I mean how come you are so kind to answer everyone who posts questions here?

 

[BerkReviewTeach]

BRT, I was just wondering, is this your full time job? I mean how come you are so kind to answer everyone who posts questions here?

It's one of a couple part time jobs. BR work stimulates my neurons more than any other job.