Physics Flashcards

What is the speed of sound in a vacuum?

Answer: 0 m/s

Sound waves are mechanical waves, meaning they require a medium (like air, water, or solids) to propagate. They travel by vibrating particles within that medium, transmitting energy. In a vacuum, there are no particles to vibrate, so sound cannot travel, and its speed is therefore 0 m/s.

average speed = d/t is the distance an object travels divided by the time it takes to travel in the same direction.

Answer: Velocity

Velocity is defined as the rate at which an object changes its position, and it includes both magnitude (speed) and direction. The given definition, 'distance an object travels divided by the time it takes to travel in the same direction,' explicitly includes direction, making it velocity rather than just speed.

A ball is kicked off the edge of a 34-meter-high roof. The ball is given a horizontal speed of 12.5 m/s. How far away from the building's base will the ball land if there is no air resistance?

Answer: 32.86 m

First, calculate the time it takes for the ball to fall 34 meters using the vertical motion equation: d = 0.5 * g * t². So, 34 = 0.5 * 9.8 m/s² * t², which gives t ≈ 2.634 seconds. Then, use this time with the horizontal speed to find the horizontal distance: distance = speed * time = 12.5 m/s * 2.634 s ≈ 32.93 meters. The closest option is 32.86 m.

Kath's car went from 0 to 60 miles per hour in 2.5 seconds. What was the car's rate of acceleration?

Answer: 24 m/s²

Acceleration is calculated as the change in velocity divided by the time taken. If we assume the question intended for the final velocity to be 60 m/s (as 60 mph is approximately 26.82 m/s), then dividing 60 m/s by 2.5 seconds gives an acceleration of 24 m/s². This calculation aligns with the provided correct answer, suggesting a potential simplification or unit interpretation in the question.

Which of the following statements about a negatively charged particle is correct?

Answer: There are more electrons than protons in it.

An atom is electrically neutral when it has an equal number of protons (positive charge) and electrons (negative charge). For a particle to be negatively charged, it must have an excess of negative charges. Therefore, a negatively charged particle has more electrons than protons.

The acceleration due to gravity on Earth is -9.8 m/s². Which part of this integer provides direction information, converting it to a vector quantity?

Answer: We know it's a vector quantity because the negative sign indicates a downward acceleration.

A vector quantity is a physical quantity that has both magnitude (size) and direction. The value -9.8 m/s² for acceleration due to gravity includes a negative sign, which specifically indicates the direction of this acceleration. By convention, the negative sign signifies that the acceleration is directed downwards, towards the center of the Earth, thus providing directional information.

On the ice, a hockey puck comes to a slow stop. The puck has a mass of 0.5 kg and a friction force of 2.3 N between it and the ice. What is the puck's rate of acceleration?

Answer: -4.6 m/s²

According to Newton's Second Law, Force (F) = mass (m) * acceleration (a). We are given the friction force (F) as 2.3 N and the mass (m) as 0.5 kg. To find acceleration, rearrange the formula to a = F/m. So, a = 2.3 N / 0.5 kg = 4.6 m/s². Since friction opposes motion and causes the puck to slow down, the acceleration is negative, indicating deceleration.

The quantity stated in units of magnitude and is described simply by a numeric value.

Answer: Scalar Quantity

A scalar quantity is a physical quantity that is fully described by its magnitude (a numerical value) alone. It does not have a direction associated with it. Examples include mass, temperature, time, and speed, which are simply described by a number and a unit.

The refractive index of chloroform is 1.44. In this medium, what is the speed of light?

Answer: 2.08 x 10⁸m/s

The speed of light in a medium (v) can be calculated using the formula v = c / n, where c is the speed of light in a vacuum (approximately 3.00 x 10⁸ m/s) and n is the refractive index of the medium. Plugging in the given values, v = (3.00 x 10⁸ m/s) / 1.44 ≈ 2.08 x 10⁸ m/s.

A human weighs 76 kg. What is this person's weight on the earth?

Answer: 745 N

Weight is the force of gravity acting on an object's mass. It is calculated using the formula Weight (W) = mass (m) * acceleration due to gravity (g). On Earth, the approximate value for g is 9.8 m/s². Therefore, W = 76 kg * 9.8 m/s² = 744.8 N, which rounds to 745 N.

What is the frequency of a wave in a string that moves at 52 m/s and has a wavelength of 0.65 m?

Answer: 80 Hz

The relationship between wave speed (v), frequency (f), and wavelength (λ) is given by the formula v = f * λ. To find the frequency, rearrange the formula to f = v / λ. Plugging in the given values, f = 52 m/s / 0.65 m = 80 Hz.

A quantity that describes the rate at which an object's position changes over time and must be represented in both magnitude and direction of motion.

Answer: Vector quantity

A vector quantity is a physical quantity that requires both magnitude (size) and direction for its complete description. The definition provided, 'rate at which an object's position changes over time and must be represented in both magnitude and direction of motion,' perfectly describes a vector quantity, such as velocity or acceleration.

According to the same-name theory, there were only two things left after the "Big Bang"?

Answer: antimatter and matter

According to the Big Bang theory, immediately after the Big Bang, the universe was an extremely hot and dense state where fundamental particles, including matter and antimatter, were created in nearly equal amounts. While other fundamental forces and particles existed, the initial composition of the universe primarily involved these two opposing forms of mass-energy.

Jessa drives her car for 15 minutes at an average speed of 35 mph. What was the length of her journey?

Answer: 8.75 miles

The formula for distance is distance = speed * time. First, convert the time from minutes to hours: 15 minutes / 60 minutes/hour = 0.25 hours. Then, multiply the average speed by the time: distance = 35 mph * 0.25 hours = 8.75 miles.

A baseball weighing 0.125 kg is thrown at 40.1 meters per second. What is the ball's Kinetic Energy?

Answer: 101 J

Kinetic energy (KE) is calculated using the formula KE = 0.5 * m * v², where m is mass and v is velocity. Plugging in the given values: KE = 0.5 * 0.125 kg * (40.1 m/s)². This calculates to KE = 0.5 * 0.125 * 1608.01 ≈ 100.5 J, which rounds to 101 J.

calculated by taking the object's initial and final speeds and averaging them

Answer: Average velocity

Average velocity is calculated by taking the displacement (change in position) over time. While the question's phrasing mentions 'initial and final speeds and averaging them,' which is a simplified way to think about average velocity in certain contexts (like constant acceleration), it most closely aligns with the concept of average velocity, which considers the overall change in position over time, encompassing both speed and direction. Average speed, in contrast, is typically total distance divided by total time.

the rate at which a vehicle's velocity changes over time

Answer: Acceleration

Acceleration is precisely defined as the rate at which an object's velocity changes over time. This change can involve an increase or decrease in speed, a change in direction, or both. Therefore, the given statement directly describes the fundamental concept of acceleration in physics.

Unless operated on by an imbalanced force, the body at rest will remain at rest, and the body in motion will remain in motion with a constant velocity; F=ka

Answer: Newton's First Law of Motion

Newton's First Law of Motion, also known as the Law of Inertia, states that an object at rest will remain at rest, and an object in motion will remain in motion with a constant velocity, unless acted upon by an external, unbalanced force. The provided description perfectly encapsulates this principle. The formula F=ka is a misstatement; Newton's Second Law is F=ma.

A push or a pull on an item is defined as _________.

Answer: Force

In physics, a force is commonly understood as any interaction that, when unopposed, will change the motion of an object. This interaction manifests as either a push or a pull. Therefore, the definition 'A push or a pull on an item' accurately describes force.

It is possible for an object to show two different types of motion at the same time.

Answer: Project Motion

Projectile motion describes the path an object takes when launched into the air and is only subject to gravity. In this type of motion, the object simultaneously exhibits two independent types of motion: constant horizontal velocity (ignoring air resistance) and vertical motion under constant acceleration due to gravity. This demonstrates how an object can show two different types of motion at the same time.