Question 1

A student touches a metal sink with her finger and notices that her finger feels cold. Which of the following statements explains this observation?

Accepted Answer

Heat energy flows from the student's finger to the metal sink because the metal, being a good conductor, quickly draws heat away from the warmer object in contact with it (in this case, the student's finger), making the finger feel cold.

Question 2

A student leaving school walks 2.5 km north and then walks 1.0 km south. What is the student's displacement?

Accepted Answer

Displacement is the shortest distance from the initial to the final position, direction included. Here, it's 2.5 km north - 1.0 km south = 1.5 km north.

Question 3

A student pushes a book across a classroom table. Which of the following statements best explains the difference between the amount of force needed to start the book moving and the amount of force needed to keep it moving?

Accepted Answer

Static friction, which must be overcome to start an object moving, is generally greater than kinetic friction, which is the frictional force encountered when an object is already in motion.

Question 4

In which of the following examples is heat transferred primarily by radiation?

Accepted Answer

Radiation is the transfer of heat through electromagnetic waves, which does not require a medium to travel through. In option D, the spoon gets warm due to the infrared radiation emitted by the flame, even though it is not directly in contact with it.

Question 5

Which of the following observations demonstrates that visible light waves are electromagnetic and not mechanical?

Accepted Answer

Electromagnetic waves, unlike mechanical waves, do not require a medium to travel through. The fact that sunlight (which is composed of visible light waves) can travel through a vacuum (space) demonstrates that these waves are electromagnetic in nature, as they can propagate without a medium.

Question 6

The momentum of an object in space is

Accepted Answer

Momentum is directly proportional to the mass of an object; the more mass an object has, the more momentum it can have at a given velocity.

Question 7

Which of the following is an example of heat transfer by conduction?

Accepted Answer

Conduction is the process of heat transfer through direct contact between materials, and an electric stove heating an iron pan is an example of this, as the heat is directly transferred from the stove to the pan through physical contact.

Question 8

The source of a sound is moving away from an observer who is standing still. How do the sound waves received by the observer compare with those emitted by the source?

Accepted Answer

When a sound source moves away from an observer, the sound waves stretch out, leading to a lower frequency being perceived by the observer. This phenomenon is known as the Doppler effect.

Question 9

Which of the following statements best describes the visible spectrum of light as seen by the human eye?

Accepted Answer

The visible spectrum of light, as perceived by the human eye, ranges from red at the lowest frequency to violet at the highest frequency. This spectrum is often represented in the color sequence of a rainbow.

Question 10

The speed of sound in a particular gas is 900 m/s. A sound wave propagating in this material has a wavelength of 15 m. What is the frequency of this sound?

Accepted Answer

The frequency of a sound wave is calculated using the formula $f = \frac{v}{\lambda}$, where $f$ is the frequency, $v$ is the speed of sound in the medium, and $\lambda$ is the wavelength. Substituting the given values, $f = \frac{900 \, \text{m/s}}{15 \, \text{m}} = 60 \, \text{Hz}$.

Question 11

Which of the following statements best describes an electromagnetic wave with a long wavelength?

Accepted Answer

Electromagnetic waves with long wavelengths have low frequencies, as wavelength and frequency are inversely related. Additionally, all electromagnetic waves, regardless of their wavelength or frequency, can travel in a vacuum.

Question 12

Based on Ohm's law, which of the following statements explains what must happen when the voltage across a resistor is decreased?

Accepted Answer

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Therefore, if the voltage across a resistor is decreased, the current through the resistor also decreases, assuming the resistance remains constant.

Question 13

Which of the following waves travels fastest?

Accepted Answer

Electromagnetic waves, which include light waves from the Sun, travel at the speed of light in a vacuum, which is approximately 299,792 kilometers per second. This speed far exceeds that of water waves, seismic waves, or sound waves in their respective mediums.

Question 14

Which of the following can carry light waves but not sound waves?

Accepted Answer

Light waves can travel through a vacuum because they are electromagnetic waves, which do not require a medium to propagate. Sound waves, on the other hand, are mechanical waves that need a medium (like air, steel, or water) to travel through, and thus cannot propagate through a vacuum.

Question 15

A sailboat travels 35 km in 5 hr. Which of the following describes the motion of the sailboat?

Accepted Answer

The sailboat's average speed is calculated by dividing the total distance traveled by the total time taken, which is 35 km / 5 hr = 7 km/hr.

Question 16

A pitcher throws a 0.15 kg baseball at 40 m/s towards the catcher. What is the momentum of the baseball while moving at 40 m/s?

Accepted Answer

The answer of A pitcher throws a 0.15 kg baseball...

Question 17

An astronaut drops a 1.0 kg object and a 5.0 kg object on the Moon. Both objects fall a total distance of 2.0 m vertically. Which of the following best describes the objects after they have fallen a distance of 1.0 m?

Accepted Answer

The answer of An astronaut drops a 1.0 kg object...

Question 18

Which of the following changes occurs as a solid is heated?

Accepted Answer

As a solid is heated, the particles gain energy and vibrate more vigorously, which increases their average molecular speed. The kinetic energy of the particles increases with temperature, leading to this effect.

Quiz 3: Hesi: Introductory Physics