course Phy 121
SEED QUESTION 6For each situation state which of the five quantities v0, vf, `ds, `dt and a are given, and give the value of each.
• A ball accelerates uniformly from 10 cm/s to 20 cm/s while traveling 45 cm.
o `dt = 10 cm/sec
o `ds = 45 cm
o Yes, you can find vAve from these two numbers. If you divide 45 cm by 10 cm/sec, then you get the vAve.
o No, you would not be able to find the `dv for this problem.
You know initial and final velocities, so you can subtract the initial from the final to find the change `dv in velocity.
Answer/question/discussion:
• A ball accelerates uniformly at 10 cm/s^2 for 3 seconds, and at the end of this interval is moving at 50 cm/s.
o A = 30 cm/sec^2
o Vf = 50 cm/sec
o No, you could not find the average velocity. To be able to, you would need the initial velocity so that you could add the final and initial velocities and divide by two.
you know a, `dt and vf. From a and `dt you can find `dv. From vf and `dv you can find v0. From v0 and vf you can find vAve, which with `dt allows you to find `ds.
o No, you would not be able to find the `dv. You would need the initial velocity to find this.
From a and `dt you can find `dv.
Answer/question/discussion:
• A ball travels 30 cm along an incline, starting from rest, while accelerating at 20 cm/s^2.
o V0 = 0 cm/sec
o `ds = 30 cm
o A = 20 cm/s^2
o Yes, you can find average velocity. With the information given, you can determine the final velocity. With this, you can add the initial and final velocities and divide by two.
o Yes, you can find the `dv. To find this number, you need the vf and v0. All you do is vf-v0.
You know v0, a and `ds. You can't directly reason out anything from these quantities. To use the definition of vAve you would need to know either vf (to be used with v0) or `dt (to be used with `ds). To use the definition of aAve you would have to know either vf (to be used with v0 to find `dv, so that you have a and `dv) or `dt (with a and `dt you can find `dv, then from v0 can find vf).
You can use the third or fourth equation of motion so get a result, but such a solution would use an equation whose intuitive meaning is not directly clear, and so does not constitute direct reasoning.
Answer/question/discussion:
Then for each situation answer the following:
• Is it possible from this information to directly determine vAve?
o Answer listed above
Answer/question/discussion:
• Is it possible to directly determine `dv?
o Answer listed above.
Answer/question/discussion:
When you submit a 'seed' question, be sure to use the form for that question. Much better you should submit it through the submit work form than not at all, but better through the intended form.
See my note and let me know if you have questions.