Physics — Semester A Practice

Question 1 of 10

TEKS 1A-4CEasy Word

A student measures the mass of a sample as 0.00284 kg. Which expression correctly represents this mass in scientific notation with proper SI units?

A28.4 × 10⁻⁴ kg

B2.84 × 10⁻² g

C2.84 × 10⁻³ kg

D2.84 × 10³ kg

Explanation

📌 Move decimal 3 places right: 0.00284 → 2.84 × 10⁻³. Coefficient must satisfy 1 ≤ a < 10, and SI mass unit is kg. Common wrong answers come from has wrong exponent sign, violates scientific notation convention, and uses wrong unit (2.84 × 10⁻² g = 0.0000284 kg, two orders off).

Question 2 of 10

TEKS 5F-5HMedium Calc Word Diagram

A 5.0-kg block on a horizontal surface is pushed with a horizontal applied force of 30 N. A frictional force of 12 N opposes motion. What is the block’s acceleration?

A2.4 m/s²

B3.6 m/s²

C6.0 m/s²

D8.4 m/s²

Explanation

📌 Net force = 30 − 12 = 18 N right. a = F_net/m = 18/5.0 = 3.6 m/s². Common wrong answers come from ignoring applied force, ignoring friction, and adding forces instead of subtracting (sign error — friction opposes motion).

Question 3 of 10

TEKS 5A-5EEasy Calc Word Diagram

The position-vs-time graph shows an object's motion. Between t = 2 s and t = 6 s, which best describes the object's motion?

AThe object is accelerating.

BThe object is moving backward.

CThe object is moving at constant velocity.

DThe object is at rest.

Explanation

📌 A horizontal line on a position-vs-time graph means position is not changing — the object is stationary (at rest). Common wrong answers come from confuses horizontal line with acceleration, confuses horizontal with constant motion, and confuses horizontal (no motion) with negative slope (backward motion).

Question 4 of 10

TEKS 5A-5EEasy Word

A cyclist travels 240 m in 30 s at constant velocity. What is her average velocity?

A8.0 m/s

B8.0 m

C7,200 m/s

D0.125 m/s

Explanation

📌 Average velocity v = d/t = 240 m / 30 s = 8.0 m/s. Common wrong answers come from multiplying (÷/× swap), taking reciprocal, and forgetting velocity units (m instead of m/s).

Question 5 of 10

TEKS 5F-5HEasy Word

According to Newton’s law of universal gravitation, if the distance between two objects is doubled while their masses remain the same, the gravitational force between them becomes:

Adoubled

Bone-fourth of the original

Chalved

Dfour times the original

Explanation

📌 F = GmM/d². Force is inversely proportional to d². Double d → d² becomes 4d² → F becomes F/4. Common wrong answers come from treats it as direct proportion, applies 1/d instead of 1/d² (forgot the square), and squares wrong direction (direct instead of inverse).

Question 6 of 10

TEKS 1A-4CEasy Word

The SI unit of electric current is:

ACoulomb

BVolt

CAmpere

DWatt

Explanation

📌 The ampere (A) is the SI unit of current. 1 A = 1 C/s. The other units name different quantities: the coulomb is charge, the volt is potential, and the watt is power.

Question 7 of 10

TEKS 5A-5EMedium Calc Word Diagram

A projectile is launched from ground level with an initial speed of 20 m/s at 30° above horizontal. What is the maximum height reached? Use g = 9.8 m/s² and ignore air resistance.

A2.55 m

B5.10 m

C15.3 m

D20.4 m

Explanation

📌 Vertical component v_iy = v sin θ = 20 × sin(30°) = 10 m/s. At max height v_y = 0. Use v_fy² − v_iy² = −2g·h → 0 − 100 = −19.6h → h = 5.10 m. Common wrong answers come from using v_iy/2 (halved velocity), using cos(30°) instead of sin(30°) — the classic sin/cos swap, and ignoring angle entirely, used full v² / 2g.

Question 8 of 10

TEKS 7D-7EMedium Calc Word Diagram

A 2.0-kg cart moving at 4.0 m/s collides with a stationary 3.0-kg cart. The two carts stick together after the collision. What is the velocity of the combined mass immediately after the collision?

A4.0 m/s

B1.6 m/s

C2.0 m/s

D6.7 m/s

Explanation

📌 Conservation of momentum (perfectly inelastic): m₁v₁ + m₂v₂ = (m₁+m₂)v_f. (2.0)(4.0) + 0 = (5.0)v_f → v_f = 1.6 m/s. Common wrong answers come from averaged velocities without mass weighting, ignoring mass conservation, and using wrong combined mass. Note: kinetic energy is NOT conserved here — 15 J is lost to heat, sound, and deformation.

Question 9 of 10

TEKS 7A-7CEasy Calc Word

A person pushes a box with a horizontal force of 50 N over a distance of 8.0 m. If the person applies the force parallel to the direction of motion, how much work is done on the box?

A3,200 J

B42 J

C400 J

D6.25 J

Explanation

📌 W = F·d·cos θ, where θ = 0° for parallel force (cos 0 = 1). W = 50 × 8.0 × 1 = 400 J. Common wrong answers come from dividing (÷ instead of ×), subtracting, and multiplying one extra time.

Question 10 of 10

TEKS 5F-5HMedium Calc Word Diagram

A 4.0-kg block slides down a frictionless ramp inclined at 30° to the horizontal. What is the magnitude of the block’s acceleration along the ramp? Use g = 9.8 m/s².

A4.9 m/s²

B8.5 m/s²

C2.0 m/s²

D9.8 m/s²

Explanation

📌 On a frictionless incline, acceleration along the ramp = g·sin θ = 9.8 × sin(30°) = 9.8 × 0.5 = 4.9 m/s². Mass cancels — same rate for any object at same angle. Common wrong answers come from unnecessarily divided by mass, using cos(30°) instead of sin(30°) — the sin/cos swap, and using full g without decomposition.

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