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MP DTE Work and Energy — practice questions

Explore 102 free Work and Energy questions in MP DTE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Work and Energy questions and exercises with answers

Showing questions 1–30 of 102.

Work done by a constant force $\vec{F}$ when the body moves through displacement $\vec{s}$ is:Read the answer and worked solution →The kinetic energy of a body of mass $m$ moving with speed $v$ is:Read the answer and worked solution →The elastic potential energy stored in a spring of spring constant $k$ when stretched by displacement $x$ is:Read the answer and worked solution →The work-energy theorem states that the net work done on a body equals:Read the answer and worked solution →Newton's FIRST law is also called the law of:Read the answer and worked solution →Newton's SECOND law states:Read the answer and worked solution →The SI unit of force is the:Read the answer and worked solution →Frictional force between surfaces ALWAYS acts:Read the answer and worked solution →Static friction f_s satisfies:Read the answer and worked solution →Kinetic friction f_k is given by:Read the answer and worked solution →For a body on a horizontal surface, the NORMAL FORCE N equals:Read the answer and worked solution →In circular motion at radius r and speed v, the centripetal acceleration is:Read the answer and worked solution →The ANGLE OF REPOSE φ is related to coefficient of friction by:Read the answer and worked solution →A 5 kg object experiences a net force of 20 N. Find its acceleration:Read the answer and worked solution →A 10 kg block on rough horizontal surface with μ_s = 0.3 just starts moving. Force applied:Read the answer and worked solution →A block of mass 2 kg on a smooth incline at 30°. Acceleration down the incline (g = 10):Read the answer and worked solution →A 1500 kg car accelerates from 0 to 30 m/s in 10 s. Average force on car:Read the answer and worked solution →In a tug-of-war, team A pulls with 200 N, team B pulls oppositely with 250 N. The rope (light) experiences net force:Read the answer and worked solution →A block of mass 5 kg on a rough incline at 37° with μ_k = 0.4. Acceleration down (g = 10, sin 37° = 0.6, cos 37° = 0.8):Read the answer and worked solution →For a body on a 60° incline with μ = 0.5, the body:Read the answer and worked solution →An object's WEIGHT on Earth (g = 10) is 50 N. Its MASS is:Read the answer and worked solution →A 5 kg block is pushed with 30 N along a frictionless surface. Acceleration:Read the answer and worked solution →A massless pulley system has two blocks: m₁ = 6 kg and m₂ = 4 kg hanging on either side. Find acceleration of system (g = 10):Read the answer and worked solution →The angle of repose between a block and an incline is 30°. The coefficient of static friction is:Read the answer and worked solution →A 100 g object is moving in a vertical circle. At the TOP of the loop, for minimum speed (string just slack), v_min equals:Read the answer and worked solution →Limiting (max static) friction is INDEPENDENT of:Read the answer and worked solution →A 4 kg mass hangs from a spring scale in an elevator. Spring reads 32 N. The elevator is:Read the answer and worked solution →A 3 kg block is pulled with F = 20 N at 30° above horizontal on rough surface (μ_k = 0.4). Find acceleration (g = 10, sin 30° = 0.5, cos 30° = 0.866):Read the answer and worked solution →In a uniform circular motion, the SPEED is constant but velocity changes direction. The acceleration:Read the answer and worked solution →A car turns a corner of radius 50 m at 20 m/s. Minimum coefficient of friction needed (g = 10):Read the answer and worked solution →

Worked practice questions

Work done by a constant force $\vec{F}$ when the body moves through displacement $\vec{s}$ is:

  1. $W = F + s$
  2. $W = F s \cos\theta$
  3. $W = F s \sin\theta$
  4. $W = F / s$
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Correct answer: B. $W = F s \cos\theta$

Work is defined as $W = \vec{F} \cdot \vec{s} = F s \cos\theta$, where $\theta$ is the angle between $\vec{F}$ and $\vec{s}$. Work is maximum ($Fs$) when force and displacement are parallel and zero when they are perpendicular ($\cos 90° = 0$). Negative work happens when force opposes motion (e.g. friction).

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The kinetic energy of a body of mass $m$ moving with speed $v$ is:

  1. $mv$
  2. $\dfrac{1}{2} m v^2$
  3. $m v^2$
  4. $\dfrac{1}{2} m v$
Show answer and solution

Correct answer: B. $\dfrac{1}{2} m v^2$

Kinetic energy: $KE = \tfrac{1}{2} m v^2$. Notice the factor of $\tfrac{1}{2}$ and the $v^2$ dependence. The quadratic dependence is why a car at 60 km/h has four times the kinetic energy of the same car at 30 km/h, not twice. Stopping distance also scales as $v^2$ for the same brakes.

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The elastic potential energy stored in a spring of spring constant $k$ when stretched by displacement $x$ is:

  1. $kx$
  2. $\dfrac{1}{2} k x^2$
  3. $k x^2$
  4. $\dfrac{1}{2} k^2 x$
Show answer and solution

Correct answer: B. $\dfrac{1}{2} k x^2$

Force needed to stretch a spring by $x$ is $F = kx$ (Hooke's law). Work done in stretching from 0 to $x$: $U = \int_0^x kx' \, dx' = \dfrac{1}{2} k x^2$. The $\tfrac{1}{2}$ shows up because force grows linearly during the stretch — average force is $kx/2$, total work is $kx/2 \cdot x = \tfrac{1}{2} k x^2$. Option A ($kx$) is the *force*, not the energy.

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