Physics force question

[victorias]

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Is there another way of solving this problem instead of using Impulse/momentum?

 

[aldol16]

No - only a different way of thinking about it. According to Newton's classical formulation of his second law, F = dp/dt. Therefore, calculate the final momentum minus the initial momentum and divide by the time interval. Another way of formulating it is: F = d(mv)/dt. Since mass does not change significantly at the macroscopic level, F = m*dv/dt. You should recognize this instantly as the textbook version of the second law, F = ma. It's just that Newton did not formulate it in this way. Thus, you could also calculate the change in velocity divided by the time interval and multiply that by mass. In other words, F = (500 kg)(20 m/s)/0.1 s.

 

[theonlytycrane]

Although the new MCAT topics list doesn't include impulse or momentum, is this still considered "fair game"?

 

[aldol16]

Although the new MCAT topics list doesn't include impulse or momentum, is this still considered "fair game"?

Well, this is just a formulation of Newton's second law... See my post above about solving it using F = ma.

 

[David513]

I understand how the equation works out such that vf is 20 m/s but, logically, how is it that if it travels 20m in 0.1s that the velocity is not 200m/s ? (20m/0.1s is 200m/1s, no?)

 

[aldol16]

I understand how the equation works out such that vf is 20 m/s but, logically, how is it that if it travels 20m in 0.1s that the velocity is not 200m/s ? (20m/0.1s is 200m/1s, no?)

The ball doesn't reach the ground in 0.1 s. In that case, the average velocity would be 200 m/s. What it's saying is that once it hits the ground, it takes 0.1 s for it to completely stop.

 

[David513]

What it's saying is that once it hits the ground, it takes 0.1 s for it to completely stop.

Ohhhh the question's grammar is confusing. I see now that the question was saying the ball hit the ground and THEN 0.1s transpired.