Question 15 — A tractor pulls a harrow - Questions at the end of the chapter - Chapter 6 - How Forces Affect Motion (Exploration)

Last updated at July 16, 2026 by

A tractor pulls a harrow (a ploughing tool) of mass m 1 with a net force F resulting in an acceleration of a 1 . The same tractor pulls a trolley of mass m 2 with a force F producing an acceleration of a 2 . If the tractor now pulls the trolley with the harrow placed on it (with the same force F ), then obtain an expression for the resulting acceleration in terms of a 1 and a 2 . Ignore friction.
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From F = ma: m 1 = F a 1 and m 2 = F a 2 .

Together the mass is m 1 + m 2 = F a 1 + F a 2 . The new acceleration is

a = F m 1 + m 2 = F F a 1 + F a 2 = 1 1 a 1 + 1 a 2 = a 1 a 2 a 1 + a 2 .

Tractor, harrow and trolley
Step Working
Mass of the harrow F = m 1 a 1 ⇒ m 1 = F a 1
Mass of the trolley F = m 2 a 2 ⇒ m 2 = F a 2
Both pulled together a = F m 1 + m 2 = F F a 1 + F a 2
Resulting acceleration a = a 1 a 2 a 1 + a 2
← Back to: 6.7 Forces Acting on a System of Objects
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