Worksheet: Inertia and Newton's First Law of Motion

In this worksheet, we will practice calculating the unknown forces acting on an object so that it remains still or moves at a constant velocity.


Three forces act on a particle, which moves with constant velocity 𝑣=(3−2)/ijms. Two of the forces are Fijk=(3+5−6)N and Fijk=(4−7+2)N. Find the third force, F.

  • A(−1+2−4)ijk N
  • B(1+3+4)ijk N
  • C(7−2+4)ijk N
  • D(−7+2+4)ijk N
  • E(−7+2−4)ijk N


While sliding a couch across a floor, the housemates Liam and Emma exert forces F and F, respectively, on the couch. F is of magnitude 130 N directed due north and F is of magnitude 180 N directed 32.0∘ east of north. A force FNet is produced by the combination of the forces exerted by Liam and Emma. In evaluating the net force, assume that east corresponds to positive displacement along the 𝑥-axis and that north corresponds to positive displacement along the 𝑦-axis.

Find FNet in component form.

  • A(84.3+243)ij N
  • B(95.0+283)ij N
  • C(98.0+230)ij N
  • D(49.5+283)ij N
  • E(63.7+304)ij N

Find the magnitude of FNet.

At what angle north of east is FNet directed?

If Liam and Emma’s housemates, Matthew and Mia, disagree with the move and want to prevent its relocation, with what combined force F should they push so that the couch does not move?

  • A(333−95.0)ij N
  • B(283+95.0)ij N
  • C−(95.0+283)ij N
  • D(195−80.5)ij N
  • E−(49.5+283)ij N


Two forces Fij=82.6√3(−)N and Fij=177.2√3(−)N act on an object. What force must be added to F and F to produce a net force of zero?

  • A259.8√3(+)ij N
  • B−259.8√3(+)ij N
  • C259.8√3(−)ij N
  • D(0(+))ij N
  • E−259.8√3(−)ij N


A force is applied to accelerate an object on a smooth icy surface. When the force stops, which of the following will be true? (Assume that friction is zero.)

  • AThe object’s speed becomes zero.
  • BThe object’s acceleration becomes zero.
  • CThe object accelerates, but in the opposite direction.
  • DThe object’s acceleration continues to increase at a constant rate.


What is Newton’s first law of motion also known as?

  • Athe law of force
  • Bthe law of gravitational attraction
  • Cthe law of inertia
  • Dthe law of action-reaction
  • Ethe law of conservation of energy

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