In: Physics
A square uniform raft, 18.1m by 18.1m, of mass 6229kg, is used as a ferryboat. If three cars, each of mass 1176kg, occupy the NE, SE, and SW corners, determine the CM of the loaded ferryboat. Use east as the positive x-axis, north as the positive y-axis and the centre of the raft as the origin.
Y coordinate?
X Coordinate
In: Physics
A 2.15-kg object hangs in equilibrium at the end of a rope (taken as massless) while a wind pushes the object with a 18.5-N horizontal force. Find the magnitude of the tension in the rope, and the rope\'s angle from the vertical. The acceleration due to gravity is 9.81 m/s2.
In: Physics
A 6 kg sled is initially at rest on a horizontal road. The sled is pulled a distance of 2.8 m by a force of 36 N applied to the sled at an angle of 30o to the horizontal. Find the change in the kinetic energy of the sled.
In: Physics
Question 1
Which of the following are true statements about the electric field?
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Equipotential lines imply magnitude and direction of the electric field. |
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The electric field inside a spherical conducting shell in 3D is zero. |
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If the electric field inside a conductor is nonzero, charges must not be moving; that is, there is a zero current. |
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The direction of the electric field is the direction of acceleration of a positive test charge. |
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The electric lines of force indicate the vector force experienced by a positive test charge released at a particular point. |
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The electric field is a vector field that is found by taking the gradient of the negative potential. |
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No electric field exists between the plates of a charged capacitor. |
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The electric field is a charge-specific force field independent of any test charge. |
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The electric field points towards a negative charge and away from a positive charge. |
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A moving charge produces a magnet anomaly. |
10 points
Question 2
Which of the following are true statements about how magnetism is like electricity?
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Single magnetic poles exist, just like single electric charges. |
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Magnetic circuits can be created, just like electric circuits. |
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The magnetic field lines around a magnet are just like the electric field lines around an electric dipole. |
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Opposites attract and likes repel; poles for magnetism, charges for electricity. |
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Cutting a magnet in half always produces two smaller magnets, just like cutting a charge in half always creates two smaller charges. |
5 points
Question 3
What is Faraday’s Law?
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It gives the direction of the induced current going through a coil when the magnetic field going through it changes. |
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The sum of all the voltage drops going around any loop in a circuit has to equal zero. |
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The sum of all the current going into a junction has to equal the sum of all the currents coming out. |
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The potential difference across a resistor is proportional to both the resistance and the current going through it |
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It defines the induced voltage across a coil when the magnetic field going through it changes. |
5 points
Question 4
How does the magnetic field in the center of a solenoid change when the number of turns of the single wire is tripled?
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It doesn’t change because the field is always zero in the center. |
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The magnetic field decreases to one third of the original. |
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It doesn’t change because it’s still only one wire. |
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It depends on the number of turns of the secondary. |
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Edge effects and self-induction keep the magnetic field to double the original. |
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The magnetic field triples. |
In: Physics
shopper in a supermarket pushes a loaded cart with a horizontal force of 8 N. The cart has a mass of 26 kg.
(a) How far will it move in 2.0 s, starting from rest? (Ignore
friction.)
1 m
(b) How far will it move in 2.0 s if the shopper places his 30 N
child in the cart before he begins to push it?
2 m
In: Physics
Prove Carnot’s Theorem: No real heat engine operating between two energy reservoirs can be more efficient than a Carnot engine operating between the same two reservoirs.
In: Physics
A). Find the two locations where an object can be placed in front of a concave mirror with a radius of curvature of 36cm such that its image is twice its size. answer in cm
B). In the case when the object is placed closer to the mirror, state whether the image is real or virtual, upright or inverted.
C). In the case when the object is placed farther to the mirror, state whether the image is real or virtual, upright or inverted.
In: Physics
Two identical + 9.0 μC point charges are initially 3.5 cm from each other.
If they are released at the same instant from rest, how fast will each be moving when they are very far away from each other? Assume they have identical masses of 3.0 mg .
Express your answer using two significant figures.
In: Physics
You're driving down the highway late one night at 20m/s when a deer steps onto the road 54 m in front of you. Your reaction time before stepping on the brakes is 0.50s, and the maximum deceleration of your car is 10m/s2.
Part A How much distance is between you and the deer when you come to a stop? Express your answer to two significant figures and include the appropriate units.
s =
Part B What is the maximum speed you could have and still not hit the deer? Express your answer to two significant figures and include the appropriate units.
v=
In: Physics
1)If the coefficient of kinetic friction between tires and dry pavement is 0.800, what is the shortest distance in which an automobile can be stopped by locking the brakes when traveling at 26.0m/s ?
2)On wet pavement the coefficient of kinetic friction may be only 0.250. How fast should you drive on wet pavement in order to be able to stop in the same distance as in part A? (Note: Locking the brakes is not the safest way to stop.)
In: Physics
A uniformly charged dielectric solid sphere of radius a = 8 cm carries a total charge Q = 5 μC. Let the potential be zero an infinite distance away.
a) [26.6] What is the potential at the surface of the sphere?
b) [26.9] Sketch the graph of the potential due to the sphere from r = 0 to r = 20 cm.
c) [26.3] What work must be done to bring a 0.2 μC point charge from infinity to a point 16 cm from the center of the sphere?
In: Physics
A flat, solid cylindrical grinding wheel with a diameter of 24.2 cm is spinning at 3000 rpm when its power is suddenly turned off. A workman continues to press his tool bit toward the wheel's center at the wheel's circumference so as to continue to grind as the wheel coasts to a stop.
If the wheel has a moment of inertia of 4.99 kg⋅m2 , the necessary torque (116 m*N ) must be exerted by the workman to bring it to rest in 13.5 s .
If the coefficient of kinetic friction between the tool bit and the wheel surface is 0.800, how hard must the workman push on the bit?(in newtons)
In: Physics
1.You are the science officer on a visit to a distant solar system. Prior to landing on a planet you measure its diameter to be 18,000 km and its rotation period to be 22.3 hours. You have previously determined that the planet orbits 2.2 X 108 km from its star with a period of 402 earth days. Once on the surface you find that the free-fall acceleration is 12.2 m/s2.
What is the mass of the planet?
What is the mass of the star?
2.In 2000, NASA placed a satellite in orbit around an asteroid. Consider a spherical asteroid with a mass of 2.7 X 1016 kg and a radius of 5.8 km.
What is the speed of a satellite orbiting 3.4 km above the surface?
What is the escape speed from the asteroid?
In: Physics
The cue ball collides with the 8-ball on a pool table. Before the collision, the 8-ball was stationary, and the cue ball was moving east with a speed of 9 m/s . After the collision, the 8-ball moves at an angle of 45 ∘ south of east with a speed of 4 m/s . Right after the collision, what is the component of the cue ball's velocity that points east? You may assume the two balls have the same mass. Right after the collision, what is the component of the cue ball's velocity that points north?
In: Physics