A 3.0 kg block and a trailing 2.0 kg block, connected by a light string, are pulled across a frictionless floor by a 25 N horizontal force applied to the 3 kg block. Calculate the tension in the string.

Dynamics Challenge #5 — Connected Bodies

Tension between
two blocks.

Dynamics Hard

Problem

A 3.0 kg block and a trailing 2.0 kg block are connected by a light string on a frictionless floor. A horizontal force of 25 N pulls the 3 kg block forward. Calculate the tension in the string.

Front block\( 3.0\ \mathrm{kg} \) (pulled)
Trailing block\( 2.0\ \mathrm{kg} \)
Applied force\( F = 25\ \mathrm{N} \)
Surfacefrictionless

The string is light and does not stretch — both blocks share one acceleration.

Hint: two free-body diagrams, one shortcut: treat the pair as a single 5 kg system to find \( a \), then isolate the trailing block — the only force on it is the tension.

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Tension betweentwo blocks.

Problem

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Tension between
two blocks.