Physics practice problems
Turn “I think” into “I know.” 100 questions across five topics. No timer. An explanation after every answer.
Sample physics problems with answers
Four example problems from each topic. Try one, then reveal the answer and the explanation.
An object moves at 3 m/s for 4 s. How far does it travel?
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Answer: 12 m. For constant velocity, distance = speed × time = 3 × 4 = 12 m.
Starting from rest, an object accelerates at 1 m/s² for 3 s. What is its speed?
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Answer: 3 m/s. v = v₀ + at = 0 + 1 × 3 = 3 m/s.
A ball is launched horizontally at 4 m/s. Ignoring air resistance, how far does it move horizontally in 2 s?
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Answer: 8 m. Horizontal velocity stays constant: x = vₓt = 4 × 2 = 8 m.
An object starts from rest with constant acceleration 2 m/s². What is its displacement after 1 s?
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Answer: 1 m. x = ½at² = ½ × 2 × 1² = 1 m.
A 2 kg object experiences a net force of 6 N. What is its acceleration?
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Answer: 3 m/s². Newton’s second law gives a = Fnet/m = 6/2 = 3 m/s².
Using g = 10 m/s², what is the potential energy of a 1 kg mass raised 3 m?
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Answer: 30 J. Eₚ = mgh = 1 × 10 × 3 = 30 J.
A 1 kg object travels at 4 m/s. What is its kinetic energy?
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Answer: 8 J. Eₖ = ½mv² = ½ × 1 × 16 = 8 J.
A block has a normal force of 20 N and static friction coefficient 0.5. What is its maximum static friction?
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Answer: 10 N. Maximum static friction = μsN = 0.5 × 20 = 10 N. Actual static friction can be smaller.
A wave has frequency 1 Hz and wavelength 3 m. What is its speed?
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Answer: 3 m/s. v = fλ = 1 × 3 = 3 m/s.
A source completes 6 cycles in 3 s. What is its frequency?
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Answer: 2 Hz. Frequency = cycles / time = 6/3 = 2 Hz.
A wave travels at 8 m/s with frequency 4 Hz. What is its wavelength?
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Answer: 2 m. λ = v/f = 8/4 = 2 m.
An ideal spring has stiffness 10 N/m and is stretched 0.2 m. What is the restoring-force magnitude?
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Answer: 2 N. |F| = k|x| = 10 × 0.2 = 2 N. The force points toward equilibrium.
A 10 Ω resistor carries 0.2 A. What is the voltage across it?
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Answer: 2 V. V = IR = 0.2 × 10 = 2 V.
A component has 4 V across it and carries 0.5 A. How much power does it transfer?
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Answer: 2 W. P = VI = 4 × 0.5 = 2 W.
Two resistors, 10 Ω and 20 Ω, are connected in series. What is their equivalent resistance?
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Answer: 30 Ω. In series, resistances add: 10 + 20 = 30 Ω.
Two equal 20 Ω resistors are in parallel. What is their equivalent resistance?
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Answer: 10 Ω. For two equal resistors in parallel, equivalent resistance is half either resistance: 20/2 = 10 Ω.
A ray in air meets a glass surface at an angle of 10° to the normal. What is its angle to the surface?
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Answer: 80 °. The surface and normal are perpendicular, so the angle to the surface is 90° − 10° = 80°.
An object is 10 cm from a lens with focal length 5 cm. What is the image distance?
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Answer: 10 cm. The object is at 2f. From 1/f = 1/dₒ + 1/dᵢ, the real image is also at 2f = 10 cm.
An image is 2 cm tall and its object is 1 cm tall. What is the magnitude of magnification?
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Answer: 2 ×. |M| = image height / object height = 2/1 = 2.
A converging lens forms an image with magnification −2 of an object 1 cm tall. What is the image-height magnitude?
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Answer: 2 cm. Image-height magnitude = |M| × object height = 2 × 1 = 2 cm. The minus sign indicates inversion.