Dabour Hub EGEgyptian Curriculum 2026/2027
2-1 (d) Acceleration as a function of velocity

2-1 (d) Acceleration as a function of velocity

Point 4 of 7 — Motion with Variable Acceleration and ForceQuestion bank: 0 questions (0 with pictures)

04 2-1 (d) Acceleration as a function of velocity

Method

  • If a=f(v), separate in time: dvf(v)=dt, or in distance: v dvf(v)=ds.
  • A resistance proportional to the velocity gives a=−kv and an exponential decay.
✍️ Worked examples

Example 10:

  • A boat of mass m moving at v0 experiences a resistance kv (where k is constant) and no other horizontal force.
  • Show that v=v0e−kt/m and that the distance travelled before it is brought to rest is mv0k.

Solution:

  • mdvdt=−kv, so ∫v0vdvv=−km∫0tdt.
  • ln⁡vv0=−ktm, so v=v0e−kt/m.
  • Using vdvds=−kvm we get dv=−km ds, so v=v0−kms.
  • v=0 when s=mv0k. The velocity tends to zero only as t→∞, but the distance is finite.

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