All Free Physics MCQs with Answers
Every Physics question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
13,934 questions · page 2 of 697
- A. 100 W
- B. 1000 W
- C. 2000 W
- D. 20000 W
Explanation: The work done is mgh, which is 200 times 10 times 10, giving 20000 J. Dividing by the 20 s taken gives 1000 W, or 1 kW.
Correct answer: 1000 W- A. total mechanical energy increases
- B. potential energy converts into kinetic energy with the total unchanged
- C. kinetic energy converts into potential energy
- D. total mechanical energy decreases
Explanation: Gravity is a conservative force, so in the absence of air resistance the sum of kinetic and potential energy stays constant while…
Correct answer: potential energy converts into kinetic energy with the total unchanged- A. 30%
- B. 43%
- C. 70%
- D. 143%
Explanation: Efficiency is useful output divided by total input times 100, which is 350 over 500 times 100, giving 70%.
Correct answer: 70%- A. 10 J
- B. 25 J
- C. 100 J
- D. 1000 J
Explanation: Potential energy gained is mgh, which is 2 times 10 times 5, giving 100 J.
Correct answer: 100 J- A. the drag force becomes zero
- B. the upward drag and upthrust together balance the weight, so the net force is zero
- C. the body stops moving completely
- D. gravity stops acting on the body
Explanation: Drag increases with speed, so the body accelerates until the retarding forces grow to match its weight, after which the acceleration is…
Correct answer: the upward drag and upthrust together balance the weight, so the net force is zero- A. the square of the speed
- B. the speed
- C. the cube of the radius
- D. the inverse of the radius
Explanation: Stokes's law gives the drag as 6 pi eta r v, so it rises in direct proportion to both the radius and the speed, provided the flow stays…
Correct answer: the speed- A. the radius of the sphere
- B. the square of the radius of the sphere
- C. the inverse of the radius
- D. the viscosity of the liquid
Explanation: Equating the weight less upthrust to the Stokes drag gives a terminal velocity proportional to r squared and inversely proportional to…
Correct answer: the square of the radius of the sphere- A. the fluid particles move in irregular, mixing paths
- B. each fluid particle follows the same smooth path as the one before it
- C. the fluid is at rest
- D. the fluid is compressible
Explanation: In laminar or streamline flow the layers slide over one another without mixing, so the velocity at any fixed point stays constant in time…
Correct answer: each fluid particle follows the same smooth path as the one before it- A. A1 v1 equals A2 v2, so the fluid speeds up where the pipe narrows
- B. A1 v1 equals A2 v2, so the fluid slows down where the pipe narrows
- C. the pressure is the same everywhere in the pipe
- D. the density changes along the pipe
Explanation: The same volume passes every cross section each second, so where the area falls the speed must rise in proportion.
Correct answer: A1 v1 equals A2 v2, so the fluid speeds up where the pipe narrows- A. half
- B. double
- C. four times
- D. unchanged
Explanation: Area depends on the square of the radius, so halving the radius quarters the area, and by the continuity equation the speed must rise by a…
Correct answer: four times- A. conservation of mass
- B. conservation of momentum
- C. conservation of energy for a flowing fluid
- D. Newton's third law
Explanation: The equation adds pressure energy, kinetic energy and potential energy per unit volume and states that the total is the same all along a…
Correct answer: conservation of energy for a flowing fluid- A. high
- B. low
- C. unchanged
- D. zero
Explanation: Since the total energy per unit volume is fixed, any gain in kinetic energy must be paid for by a fall in pressure energy.
Correct answer: low- A. air moves faster over the curved upper surface, lowering the pressure there
- B. air moves faster under the wing
- C. the wing is lighter than air
- D. the engines push the wing upwards
Explanation: The aerofoil shape makes the air travel further and faster across the top, so by Bernoulli's principle the pressure above is lower than…
Correct answer: air moves faster over the curved upper surface, lowering the pressure there- A. the temperature rise in a constriction
- B. the pressure difference between a wide section and a narrow section
- C. the weight of the fluid
- D. the colour change of the fluid
Explanation: The fluid speeds up in the throat, so its pressure falls, and measuring that pressure drop with a manometer gives the speed through the…
Correct answer: the pressure difference between a wide section and a narrow section- A. N s per m squared
- B. N per m squared
- C. N m
- D. m squared per s
Explanation: Viscosity is defined through the relation between shear stress and velocity gradient, giving units of newton second per square metre…
Correct answer: N s per m squared- A. increases
- B. decreases
- C. stays the same
- D. becomes zero
Explanation: Heating gives the molecules enough energy to slip past one another more easily, weakening the intermolecular attractions that resist flow…
Correct answer: decreases- A. where the artery is narrowest
- B. where the blood flows fastest
- C. where the vessel is widest and the blood moves slowest
- D. at the capillaries
Explanation: Bernoulli's principle applies inside the body as well: where the cross section is large the speed is low and more of the energy remains as…
Correct answer: where the vessel is widest and the blood moves slowest- A. the weight of the body
- B. the weight of the fluid displaced by the body
- C. the volume of the body
- D. the density of the fluid
Explanation: This is Archimedes's principle, and the upthrust arises because pressure increases with depth, so the upward force on the bottom of the…
Correct answer: the weight of the fluid displaced by the body- A. the same terminal velocity
- B. a lower terminal velocity
- C. a higher terminal velocity
- D. no terminal velocity
Explanation: Terminal velocity depends on the difference between the density of the sphere and that of the fluid, so a denser sphere needs a larger…
Correct answer: a higher terminal velocity- A. falls, because the larger area increases the drag at a given speed
- B. rises, because the parachute adds weight
- C. is unchanged
- D. becomes zero immediately
Explanation: Opening the canopy multiplies the effective area and therefore the drag, so the forces balance again at a much lower speed and the diver…
Correct answer: falls, because the larger area increases the drag at a given speed