A small dust particle of mass 7.90 × 10-6 g is being observed under a magnifying lens. Its position is determined to within 0.0050 mm. (1 y = 3.156 × 107 s, h = 6.626 × 10-34 J ? s)
(a) Find the minimum uncertainty in its velocity implied by the uncertainty in its position.
(b) Assuming the dust particle is moving at the speed you just found, how many years would it take for the particle to move 1.0 mm?
What will be an ideal response?
Answer: (a) 8.4 × 10-21 m/s (b) 3.8 × 109 y
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A bar (L = 80 cm) moves on two frictionless rails, as shown, in a region where the magnetic field is uniform (B = 0.30 T) and into the paper. If v = 50 cm/s and R = 60 m?, what is the magnetic force on the moving bar?
a.
0.48 N to the right
b.
0.48 N to the left
c.
0.32 N to the left
d.
0.32 N to the right
e.
None of the above
A concave mirror has a focal length of 20 cm. What is the position (in cm) of the object if the image is upright and is two times larger than the object?
a. 30 b. 20 c. 10 d. 40 e. 60
The first living organisms probably resembled
A) single-celled eukaryotes B) multicellular eukaryotes C) single-celled prokaryotes D) multicellular prokaryotes
Studies from ________ led to the discovery of "dark energy."
A) Type II supernovae in the Large Magellanic Cloud B) Cepheid variables in the Virgo Cluster C) the COBE microwave ripples D) the gravitational lensing by MACHOs E) Type I supernovae at very large redshifts