Which quantity is a vector?

• electric field

• electric potential difference

• electric charge

• electric power

Answer explanation

The electric field is a vector quantity because it has both magnitude and direction, representing the force per unit charge. In contrast, electric potential difference, charge, and power are scalar quantities.

Tags

NGSS.HS-PS2-4

NGSS.HS-PS3-5

What is the magnitude of the eastward component of the velocity of an airplane flying at 612 kilometers per hour in a direction 40.0° north of east?

• 393 km/h

• 469 km/h

• 799 km/h

• 952 km/h

Answer explanation

To find the eastward component, use the formula: V_east = V * cos(θ). Here, V = 612 km/h and θ = 40°. Thus, V_east = 612 * cos(40°) ≈ 469 km/h, which is the correct answer.

A car, initially traveling at 25 meters per second, is uniformly brought to rest as the brakes are applied over a distance of 40. meters. The magnitude of the average acceleration of the car while braking is

• 0.31 m/s²

• 0.63 m/s²

• 7.8 m/s²

• 16 m/s²

Answer explanation

To find the average acceleration, use the formula: a = (v_f^2 - v_i^2) / (2 * d). Here, v_f = 0 m/s, v_i = 25 m/s, and d = 40 m. Plugging in the values gives a = (0 - 25^2) / (2 * 40) = -0.63 m/s². The magnitude is 0.63 m/s².

Tags

NGSS.HS-PS2-1

A brick starts from rest and falls freely from the top of a building to the ground. As the brick falls, its acceleration

• increases and its speed increases

• increases and its speed is constant

• is constant and its speed increases

• is constant and its speed is constant

Answer explanation

The brick experiences constant acceleration due to gravity (approximately 9.81 m/s²) as it falls. Consequently, its speed increases continuously until it hits the ground, making the correct choice: is constant and its speed increases.

Tags

NGSS.HS-PS2-1

Which object has the greatest inertia?

• a 0.10-kg baseball traveling at 30. m/s

• a 70-kg sprinter traveling at 10. m/s

• a 1000-kg car traveling at 50. m/s

• a 2000-kg truck traveling at 20. m/s

Answer explanation

Inertia depends on mass; the greater the mass, the greater the inertia. The 2000-kg truck has the highest mass among the options, making it the object with the greatest inertia, regardless of its speed.

Tags

NGSS.HS-PS2-1

An unbalanced force is always necessary to

• keep a body at rest

• keep a body moving with constant velocity

• change the speed of a body

• change the position of a body

Answer explanation

An unbalanced force is necessary to change the speed of a body, as it alters the body's state of motion. In contrast, balanced forces keep a body at rest or moving at constant velocity.

Tags

NGSS.HS-PS2-1

Space probes launched from Earth send information back to Earth from space in the form of

• mechanical waves

• sound waves

• longitudinal waves

• electromagnetic waves

Answer explanation

Space probes communicate with Earth using electromagnetic waves, which include radio waves. Mechanical and sound waves require a medium to travel, which is not available in the vacuum of space.

Tags

NGSS.HS-PS4-3

NGSS.HS-PS4-5

A ball is thrown from level ground at an angle of 55° above the horizontal and lands on level ground. Neglecting friction, if the ball is thrown again at the same angle but with a larger initial speed, the ball will travel

• higher and the same distance horizontally

• to the same maximum height and farther horizontally

• both higher and farther horizontally

• to the same maximum height and the same distance horizontally

Answer explanation

When the ball is thrown with a larger initial speed, both its maximum height and horizontal distance increase. Thus, it will travel both higher and farther horizontally, making 'both higher and farther horizontally' the correct choice.

What is the weight of a 60.0-kilogram student on the surface of Earth?

• 0.164 N

• 6.12 N

• 60.0 N

• 589 N

Answer explanation

The weight of an object is calculated using the formula: weight = mass × gravity. For a 60.0 kg student on Earth, weight = 60.0 kg × 9.81 m/s² = 588.6 N, which rounds to 589 N.

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-4

A 120-newton box is pulled by a 48-newton horizontal force across a horizontal surface at constant velocity. The coefficient of kinetic friction between the box and the horizontal surface is

• 0.041

• 0.40

• 0.67

• 2.5

Answer explanation

The box is pulled at constant velocity, meaning the pulling force equals the frictional force. Using F_friction = μ_k * N, where N = weight (120 N), we find μ_k = 48 N / 120 N = 0.40. Thus, the coefficient of kinetic friction is 0.40.

Tags

NGSS.HS-PS2-1