# Calculating acceleration of plane when given mass, friction force and Vi

## Homework Statement

A 2000 kg plane is landing at an airfield with an initial speed of 50 m/s. The force of friction is 1/4 the weight of the plane. What is the acceleration of the plane?

## Homework Equations

Fnet = ma

Fnet = something - ff

## The Attempt at a Solution

2000a = thing I don't know - ff, which is 500 n

So

2000a = ? - 500N

What force am I missing?

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haruspex
Homework Helper
Gold Member
What force am I missing?
Why are you convinced you are missing a force?

SteamKing
Staff Emeritus
Homework Helper

## Homework Statement

A 2000 kg plane is landing at an airfield with an initial speed of 50 m/s. The force of friction is 1/4 the weight of the plane. What is the acceleration of the plane?

## Homework Equations

Fnet = ma

Fnet = something - ff

## The Attempt at a Solution

2000a = thing I don't know - ff, which is 500 n

So

2000a = ? - 500N

What force am I missing?
You're missing the fact that 500 N is ≠ 1/4 of the weight of the plane. Remember, 2000 kg is the mass of the plane, not its weight.