Question 1

Which of these happens when one kilogram of uranium undergoes nuclear fission?

Accepted Answer

The answer of Which of these happens when one kilogram...

Question 2

Velma, who is moving past you at a high rate of speed, holds a meter stick and a standard kilogram. Is it possible that your measurements could show the standard kilogram to have a mass of 2 kg while the meter stick still has its normal length of 1 m?

Accepted Answer

The length of an object is measured parallel to its direction of motion, while the mass of an object is measured perpendicular to its direction of motion.

Question 3

You are inside a jet plane moving at a constant velocity. You toss a rock straight up in the air, and then you keep your hand at the point of release. The rock comes down in your hand. This example illustrates

Accepted Answer

The principle of relativity states that the laws of physics are the same in all inertial frames of reference. Since the plane is moving at a constant velocity, it is an inertial frame, and the rock behaves as if the plane were at rest.

Question 4

The two great theories of 20th- century physics are the theory of relativity and

Accepted Answer

The two great theories of 20th-century physics are the theory of relativity, developed by Albert Einstein, and quantum theory, which describes the behavior of matter and energy at the smallest scales.

Question 5

We proved, using Einstein's two basic principles, that if Velma is moving past Mort then Mort should observe Velma's clock to go slow. This behavior of Velma's clock occurs because, as observed by Mort,

Accepted Answer

The light beam in Velma's light-clock travels further than 300,000 km during one of Velma's ticks due to the relative motion, leading to time dilation as observed by Mort.

Question 6

The post- Newtonian age began in 1900 when

Accepted Answer

The answer of The post- Newtonian age began in 1900...

Question 7

What does E = mc²say-- that all energy has mass, or that all mass has energy?

Accepted Answer

The answer of What does E = mc²say-- that...

Question 8

Velma passes Mort at a high speed. Each holds a meter stick, oriented perpendicular to the direction of relative motion. Mort observes that

Accepted Answer

The answer of Velma passes Mort at a high speed....

Question 9

Velma is in a train moving eastward at 20 m/s. She throws a ball toward the rear of the train, throwing it at her normal "throwing speed" of 20 m/s. What is Mort's observation, regarding the ball?

Accepted Answer

The answer of Velma is in a train moving eastward...

Question 10

Velma and Mort pass each other, in rocket ships, at a relative velocity of half of lightspeed. Velma has an ice cream cone which will melt in 5 minutes if not refrigerated. She removes her cone from the refrigerator, and allows it to melt. According to Velma, how long does it take for her own cone to melt?

Accepted Answer

The time dilation effect of special relativity states that moving clocks run slower than stationary clocks. In this case, Velma is moving relative to the ice cream cone, so her clock will run slower than the clock on the cone. This means that the cone will melt more slowly for Velma than it would for someone who was stationary relative to the cone. Therefore, it will take Velma more than 5 minutes to melt her cone.

Question 11

The center of our galaxy is 30,000 light years away. Could a person possibly travel there in her own lifetime?

Accepted Answer

Traveling at nearly lightspeed would result in significant time dilation, allowing the traveler to experience a much shorter duration than 30,000 years.

Question 12

Velma is in a train headed north past Mort at 30 m/s. Velma has a slingshot that can shoot pebbles at 40 m/s. Velma shoots a pebble toward the rear of the train. Velma observes the pebble's velocity to be

Accepted Answer

The answer of Velma is in a train headed north...

Question 13

Einstein believed that the principle of relativity should apply to Maxwell's theory of electromagnetism. Which basic principle or law did this lead Einstein to propose?

Accepted Answer

Einstein proposed the constancy of the speed of light as a fundamental postulate of his theory of special relativity, ensuring that Maxwell's equations hold true in all inertial frames.

Question 14

Velma passes Mort at a high speed. Velma and Mort each have identical light- clocks. Mort and Velma both observe both clocks to "tick" simultaneously at 12 noon on both clocks. Mort observes that Velma's next tick occurs

Accepted Answer

Due to time dilation in special relativity, Mort will observe Velma's clock ticking slower than his own, so Velma's next tick will occur after Mort's clock ticks.

Question 15

A meter stick having a rest mass of 1 kg moves past you. Your measurements show it to have a mass of 2 kg and a length of 1 m. How is the stick oriented, as observed by you?

Accepted Answer

The length contraction only occurs in the direction of motion. Since the length is measured as 1 m (the same as its rest length), the stick must be oriented perpendicular to its direction of motion.

Question 16

Einstein proposed two basic principles or laws as the foundation of his special theory of relativity. One of these principles is intuitively plausible, while the other seems quite implausible or odd to our intuitions. The principle that is intuitively plausible is

Accepted Answer

The principle of relativity is intuitively plausible as it states that the laws of physics are the same in all inertial frames of reference, which aligns with our everyday experiences of consistent physical laws.

Question 17

The graph above shows the relativity of space. Suppose that Velma observes Mort's automobile as she passes it at 60% of lightspeed. She passes lengthwise over the automobile. Mort's automobile is 4 meters long as measured by Mort. How long is it as measured by Velma?

Accepted Answer

According to the theory of relativity, length contraction occurs when an object is moving relative to an observer. The formula for length contraction is L = L0 * sqrt(1 - v^2/c^2), where L0 is the proper length, v is the velocity, and c is the speed of light. Plugging in the values, L = 4 * sqrt(1 - (0.6)^2) = 4 * sqrt(0.64) = 4 * 0.8 = 3.2 meters.

Question 18

Very early in his thinking about relativity, Einstein asked himself what a person would observe if he or she kept up with a lightbeam. In answer to this question, the theory of relativity states that

Accepted Answer

According to the theory of relativity, nothing with mass can travel at the speed of light, so the question of keeping up with a light beam is not valid.

Question 19

According to Einstein's E=mc²and the "field view of reality,"

Accepted Answer

Einstein's equation E=mc² implies that mass and energy are interchangeable, suggesting that an atom's mass can arise from the energy of its fields. Additionally, the field view of reality posits that atoms are not solid objects but are composed of fields, making them mostly empty space.

Question 20

"Unless you look outside, you cannot tell how fast you are going." This is one way of stating

Accepted Answer

The statement reflects the principle of relativity, which suggests that without an external reference point, you cannot determine your state of motion. This principle is foundational in both Galileo's and Einstein's theories of relativity.

Quiz 10: The Special Theory of Relativity