Mechanics common mistakes

Common mistakes

• Quantities and units in mechanics common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: P1 Understand and use fundamental quantities and units in the SI system, including length, time and mass; understand and use derived quantities and units including velocity, acceleration, force, weight and moment..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Quantities and units in mechanics.

• Kinematics language common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: Q1 Understand and use the language of kinematics, including position, displacement, distance travelled, velocity, speed and acceleration..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Kinematics language.

• Kinematics graphs common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: Q2 Understand, use and interpret graphs in kinematics for motion in a straight line, including displacement against time with gradient interpretation and velocity against time with gradient and area interpretation..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Kinematics graphs.

• Constant acceleration common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: Q3 Understand, use and derive the formulae for constant acceleration for motion in a straight line and extend to two dimensions using vectors..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Constant acceleration.

• Calculus in kinematics common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: Q4 Use calculus in kinematics for motion in a straight line, including v = dr/dt, a = dv/dt = d^2r/dt^2, r = integral of v dt and v = integral of a dt, and extend to two dimensions using vectors..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Calculus in kinematics.

• Projectiles common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: Q5 Model motion under gravity in a vertical plane using vectors, including projectiles..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Projectiles.

• Force and Newton's first law common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: R1 Understand the concept of a force and understand and use Newton's first law..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Force and Newton's first law.

• Newton's second law common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: R2 Understand and use Newton's second law for motion in a straight line, restricted to forces in two perpendicular directions or simple cases of forces given as two-dimensional vectors, and extend to situations where forces need to be resolved in two dimensions..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Newton's second law.

• Weight and gravity common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: R3 Understand and use weight and motion in a straight line under gravity; use gravitational acceleration g and its value in SI units to varying degrees of accuracy; understand that g is not a universal constant and depends on location..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Weight and gravity.

• Newton's third law and equilibrium common mistake 1

  Writing a final answer without showing the method that justifies it. This can weaken answers for: R4 Understand and use Newton's third law; use equilibrium of forces on a particle and motion in a straight line, restricted to forces in two perpendicular directions or simple two-dimensional vector cases; apply to smooth pulleys and connected particles; resolve forces in two dimensions; use equilibrium of a particle under coplanar forces..

  Fix itShow the method first, then give the final answer in the required form. Apply this directly to Newton's third law and equilibrium.