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# Apply: conservation of momentum

NGSS.HS: HS‑PS2‑2, HS‑PS2‑3, HS‑PS2.A.3, HS‑PS2.A, HS‑PS2
You might need: Calculator

## Problem

A person applies a 20, start text, N, end text force for 2, start text, s, e, c, o, n, d, s, end text to a shopping cart with an initial momentum of minus, 60, start text, k, g, end text, dot, start fraction, start text, m, end text, divided by, start text, s, end text, end fraction to slow it down.
A person walks and pushes a shopping cart. An arrow points to the right, in the direction the person walks, and a label reads external force of twenty Newtons for two seconds. An arrow points to the left over the shopping cart and reads negative sixty kilogram meters per second.
What is the change in momentum of the shopping cart?