ASVAB · Force and Motion

Two objects collide and stick together. Object A (2 kg, 6 m/s) hits stationary Object B (4 kg). What is their combined velocity after the collision?

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Correct answer

2 m/s

A 2 m/s
B 6 m/s
C 1 m/s
D 3 m/s

Why this is the answer

CONSERVATION OF MOMENTUM (perfectly inelastic collision): Total momentum before = Total momentum after. Momentum = mass × velocity. Before: Object A: 2 kg × 6 m/s = 12 kg·m/s; Object B: 4 kg × 0 = 0. Total before: 12 kg·m/s. After: Combined mass = 2 + 4 = 6 kg. 6 kg × v = 12 kg·m/s. v = 12 ÷ 6 = 2 m/s. Note: kinetic energy is NOT conserved in inelastic collisions (some becomes heat/sound/deformation). Momentum IS always conserved in all collisions.

Source: ASVAB MC, Momentum — Conservation

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About this topic: Force and Motion

Force and motion questions cover Newton's laws, friction, gravity, acceleration and momentum, usually as pictures of objects being pushed, pulled, dropped or balanced. Identify every force acting before deciding what the object will do. This is one of 13 Mechanical Comprehension questions on force and motion, each with a full explanation on a single study page.

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Two objects collide and stick together. Object A (2 kg, 6 m/s) hits stationary Object B (4 kg). What is their combined velocity after the collision?

Why this is the answer

Practice more questions

About this topic: Force and Motion

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