A farsihted man uses eyeglasses with a refractive power of 3.09 diopters. Wearing the glasses 0.027 m from his eyes, he is able to read books held no closer than 0.250 m from his eyes. He would like a prescription for contact lenses to serve the same purpose. What is the correct contact lens prescription, in diopters?
In: Physics
A glass tube (open at both ends) of length L is
positioned near an audio speaker of frequency f = 600 Hz.
For what values of L will the tube resonate with the
speaker? (Assume that the speed of sound in air is 343 m/s.)
m (lowest possible value)
m (second lowest possible value)
m (third lowest possible value)
In: Physics
Two neutron stars are separated by a distance of 1.0x1010 m. They each have a mass of 1.0x1030 kg and a radius of 500000 m. They are initially at rest with respect to each other. As measured from the rest frame, how fast are they moving when their separation has decreased to one-half its initial value?
___________ m/s (The correct answer for this is 81663.94319)
How fast are they moving when they collide?
___________ m/s (I can't figure out this answer.)
Please use my numbers to work out the solution. Thanks!
In: Physics
The mass of carbon in an animal bone fragment found in an archeology site is 200 g. If the bone registers an activity of 16 Bq, what is its age? Note: 12.0 g of C126 contains 6.02 x 1023 atoms and C146 / C126 ~ 1.3x10-12
In: Physics
Section 1
How far from a -7.40 μC point charge must a 2.00 μC point charge be placed in order for the electric potential energy of the pair of charges to be -0.500 J ? (Take the energy to be zero when the charges are infinitely far apart.)
d = ____ m (The Answer Is Not 0.52 m)
Section 2
A point charge has a charge of 2.50×10−11 C .
Part A
At what distance from the point charge is the electric potential 84.0 V ? Take the potential to be zero at an infinite distance from the charge.
d = ___ m
Part B
At what distance from the point charge is the electric potential 25.0 V ? Take the potential to be zero at an infinite distance from the charge.
d = ___ m
In: Physics
A ball is tossed from an upper-story window of a building. The ball is given an initial velocity of 7.60 m/s at an angle of 15.0
In: Physics
Describe rotameter-type flowmeters, explain how they work, and compare them with
Venturi flowmeters
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Two balls (solid spheres) have the same radius and the same rotational kinetic energy. If the ratio of their masses is
| m1 |
| m2 |
=
| 4 |
| 1 |
, what is the ratio of their angular velocities?
In: Physics
A mass m = 12 kg rests on a frictionless table and accelerated
by a spring with spring constant k = 5249 N/m. The floor is
frictionless except for a rough patch. For this rough path, the
coefficient of friction is μk = 0.49. The mass leaves
the spring at a speed v = 3.2 m/s.
A)How much work is done by the spring as it accelerates the
mass?
B)How far was the spring stretched from its unstreched
length?
C)
The mass is measured to leave the rough spot with a final speed vf = 1.9 m/s.
How much work is done by friction as the mass crosses the rough
spot?
D)What is the length of the rough spot?
E)In a new scenario, the block only makes it (exactly) half-way
through the rough spot. How far was the spring compressed from its
unstretched length?
F)In this new scenario, what would the coefficient of friction of
the rough patch need to be changed to in order for the block to
just barely make it through the rough patch?
In: Physics
a 2kg mass lying at rest at the origin is subjected to a force of 10 N directed along the positive X-axis and another force of 10 N along the positive y-axis. How far from the origin will the mass be in 5 seconds?
In: Physics
You have been called to testify as an expert witness in a trial involving a head-on collision. Car A weighs 1515 lb and was traveling eastward. Car B weighs 1125 lb and was traveling westward at 41.0 mph. The cars locked bumpers and slid eastward with their wheels locked for 21.5 ft before stopping. You have measured the coefficient of kinetic friction between the tires and the pavement to be 0.750. How fast (in miles per hour) was car A traveling just before the collision? (This problem uses English units because they would be used in a U.S. legal proceeding.)
In: Physics
A mountain climber jumps a 3.2m -wide crevasse by leaping horizontally with a speed of 7.1m/s . If the climber's direction of motion on landing is -45?, what is the height difference between the two sides of the crevasse?
In: Physics
A rock is suspended by a light string. When the rock is in air, the tension in the string is 45.0 N . When the rock is totally immersed in water, the tension is 29.2 N . When the rock is totally immersed in an unknown liquid, the tension is 21.0 N .
What is the density of the unknown liquid?
In: Physics