A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case. Case A: Thrown straight up. Case B: Thrown straight down
Case C: Thrown out at an angle of 45° above horizontal. Case D: Thrown straight out horizontally. In which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance? A) Case A
B) Case B
C) Case C
D) Case D
E) The speed will be the same in all cases.
E
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A mass m = 4.7 kg hangs on the end of a massless rope L = 2.05 m long. The pendulum is held horizontal and released from rest.
1) How fast is the mass moving at the bottom of its path?
2) What is the magnitude of the tension in the string at the bottom of the path?
3) If the maximum tension the string can take without breaking is Tmax = 382N, what is the maximum mass that can be used (Assuming that the mass is still released from the horizontal and swings down to its lowest point.)
4) Now a peg is placed 4/5 of the way down the pendulum's path so that when the mass falls to its vertical position it hits and wraps around the peg. As it wraps around the peg and attains its maximum height it ends a distance of 3/5 L below its starting point (or 2/5 L from its lowest point). How fast is the mass moving at the top of its new path (directly above the peg)?
5) Using the original mass of m = 4.7 kg, what is the magnitude of the tension in the string at the top of the new path (directly above the peg)?
An iron atom’s nucleus has 26 protons and 30 neutrons. A helium atom’s nucleus has 2 protons and 2 neutrons. Solid iron is much denser than helium gas. How does the total positive charge in a gram of iron compare to that of a gram of helium?
A. Iron has more positive charge than helium per gram. B. Iron has the same positive charge as helium per gram. C. Iron has less positive charge than helium per gram. D. There is not enough information to tell.
An earthquake of what magnitude on the Richter scale is the smallest felt by humans?
a. 1 b. 2 c. 0 d. 4
A conducting bar moves as shown near a long wire carrying a constant 80-A current. If a = 1.0 mm, b = 20 mm, and v = 5.0 m/s, what is the potential difference, Va ? Vb?
a.
?0.24 mV
b.
+0.24 mV
c.
?0.19 mV
d.
+0.19 mV
e.
?0.76 mV