Homework Questions/Writing Assignments Flashcards
(10 cards)
Lisa travels along a circle centred on Bart. Does Lisa’s distance from and position relative to Bart change with time?
If Lisa travels in a perfect circle, then her distance from Bart wouldn’t change. However, her position relative to him would change with time.
The road runner R has a greater acceleration than the coyote C. If the net force on R and C is the same, do they have the same mass?
R and C would not have the same mass; R’s mass would be less than C’s. If FNET/a = m, R has a greater acceleration than C, and they have the same net force, so C would have a greater mass.
A book is subjected to forces of 5 newtons to the left and 6 newtons to the right. Does the book move?
Yes, the book would move left, because it has a greater force acting on it from the right.
Suppose the Earth’s radius is made bigger, but its mass is kept the same. Would the acceleration due to gravity at a particular location on the surface of the Earth change?
If the Earth’s radius is made bigger but its mass kept the same, the acceleration due to gravity would decrease. This can be proved using Newton’s theory of gravity and the equation . If the distance between the centre of the earth and an object on its surface (represented by R) were to increase, then according to the equation, FG would equate to a smaller number.
Describe the electric field due to a proton at a point far from the proton.
This proton’s electric field would have a weak affect on any particle far away from it. It would weakly repel other protons and weakly attract electrons. Distance is the biggest factor in this; if the proton were closer to the given point, its electric field would have a stronger and more noticeable effect.
A small compass is brought close to a straight wire. A steady current is then allowed to pass through the wire. Does the compass needle change its direction?
The compass needle does change its direction; it changes according to Maxwell’s fourth equation that says an electric current creates a magnetic field. The compass needle will move to point toward this magnetic field; the point of the needle is attracted to the field created by the current passing through the wire.
The speed of light in water is about 2.3x108 m/s. Suppose an electron travels through water at about 2.4x108 m/s. Is this possible according to Special Relativity?
According to Special Relativity, it is possible for an electron in water to move faster than light in water. Special Relativity says that light moves at a constant speed, c, through a vacuum. However, when travelling through a substance like water, light slows down and it is possible to fire electrons that move at a greater speed.
The acceleration due to gravity near the surface of the Earth is about 10 m/s2. How does General Relativity qualitatively explain this observation?
The Earth is an object with great mass, so it bends space-time around it. Gravity is what we feel due to this bending. Objects that move in the curved space-time around the Earth move on a geodesic, which is the shortest distance between two places. So, when we observe an object accelerating toward the Earth, it is due to the fact that it’s free-falling on a geodesic in curved space-time.
Does an incandescent light bulb emit X-rays when it operates normally?
Incandescent light bulbs do not emit x-rays. This is because they create light by heating coils of filament using electric currents until they are white-hot. Unlike the sun, which emits all kinds of rays, these kinds of light bulbs can only emit visible light.
Do the protons confined in the nucleus of a helium atom behave like classical particles?
These protons do not act like classical particles. Protons are positively charged, and so in classical mechanics, they would repel one another. But in the nucleus, protons stay together in a confined space, held by Strom forces. So they are not classical particles.
