course PHY 201
For 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.
answer/question/discussion:
Given:
v0 = 10cm/s
vf = 20cm/s
‘ds = 45cm
Calculated:
‘dv = 20 – 10 = 10cm/s
Vavg = (20 + 10)/2 = 15cm/s
A = ‘dv/’dt = 10/3s = 3.33cm/s/s
‘dt = ‘ds/vavg = 45cm / 15cm/s = 3s
• 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.
answer/question/discussion:
Given:
A = 10cm/s/s
‘dt = 3s
Vf = 50cm/s
Calculated:
‘dv = a * ‘dt = 10 * 3 = 30 cm/s
V0 = vf – ‘dv = 50 - 30 = 20cm/s
Vavg = (vf + v0) /2 = (50 + 20) /2 = 35cm/s
‘ds = vavg *’dt = 35cm/s * 3s = 105cm
• A ball travels 30 cm along an incline, starting from rest, while accelerating at 20 cm/s^2.
answer/question/discussion:
Given:
‘ds = 30cm
v0 = 0s
a = 20cm/s^2
Calculated:
Vf = sqr root( v0^2 + 2*a*’ds) = sqr rt( 2 * 20 * 30) = 34.64cm/s
Vavg = (34.64 + 0)/2 = 17.32cm/s
‘dt = ‘ds / vavg = 30/ 17.32 = 1.73s
Then for each situation answer the following:
• Is it possible from this information to directly determine vAve?
answer/question/discussion:
It is not possible to directly determine vAve in any of these because none give both’ds and ‘dt. Vave can be estimated by taking the average of the initial and final velocities.
• Is it possible to directly determine `dv?
answer/question/discussion:
‘dv can be directly determined in the first 2 problems.
It cannot be directly determined for the last problem because vf has to be calculated.
&#Very good responses. Let me know if you have questions. &#