#$&*
course Phy 201
ProblemDo the following:
• Make up a problem for situation # 10, and solve it using direct reasoning.
• Accompany your solution with an explanation of the meaning of each step and with a flow diagram.
• Then solve the same problem using the equations of uniformly accelerated motion.
• Make up a problem for situation # 8, and solve it using the equations of uniformly accelerated motion.
10
If a book is dropped from 20 feet in the air and takes 10 s to reach the ground, what was its initial and final velocity?
gravity = 32.2 ft/sec^2
ds = V0 * dt + 1/2 a * dt^2
20 ft = V0 * 10s + 1/2 32/2 ft/s^2 * (10s)^2
20 ft = V0 * 10s + 1610 ft
V0 = -159 ft/sec
Vf = V0 *+ a *dt
Vf = -159 ft/s + 32.2 ft/s^2 * 10 s
Vf = -159 ft/s + 322 ft/s
Vf = 163 ft/s
8
If a car accelerates 10 m/s^2 and reaches a vf of 15 m/s in 300 m, how long would it take to reach vf?
vf = v0 + a * dt
15 m/s = 0 + 10 m/s^2 * x s
15 m/s = 10 m/s * x
x = 1.5 s
???? I am confused by this last section."
@&
Good on the first problem.
On the last problem you know vf, a and `ds. Use the fourth equation of motion to find vf. Then figure out the required `dt.
Alternatively you could use the third equation of motion and solve for `dt. The equation is quadratic in `dt, so the fourth equation might be easier to interpret.
*@
@&
&#Please see my notes and submit a copy of this document with revisions, comments and/or questions, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
Be sure to include the entire document, including my notes. &#
*@