Dynamics

Mass & Acceleration

2nd Law of Motion

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Do Now

Do Now warm-up prompt

Ranking Task

Try it

Rank the Net Force on each object
from greatest to least.

Ranking task diagram of objects to rank by net force

June 2015

Simulating Zero g

What's a Vomit Comet? — NASA

NASA KC-135 zero-g training aircraft
2008 Sandia Corporation

NASA and B.Y.U.

School blocks YouTube? Download files below.

Vomit Comet 1  |  Vomit Comet 2

The Formula

ms2 a = Fnet m NKg

Mass & Acceleration Are Inversely Proportional

The acceleration a given force will produce on an object is inversely proportional to the mass of the object

[ Flash ]

Object A

F = 10 nt
m = 2 kg

a = 5 m/s2

Object B

F = 10 nt
m = 4 kg

a = ?

↓

Object A

a = 5 m/s2

Object B

a = 2.5 m/s2

Graph of acceleration versus mass

Double the mass,
half the acceleration

a m
×2×1/2
×1/2×2
×1/3×3
×3×1/3
×1/4×4
×3/2×2/3

“Why do all bodies accelerate at a rate of 10 m/s2 (9.8 m/s2)”
(neglecting friction)

↓
Gravity and mass diagram
Paul Hewitt

Inertial Mass

Solve for m — finding mass using motion and force

m = Fnet a

Force versus acceleration plot

What is the mass of the body
that produced the plot above?

↓

m = Fnet a = 6 N 2 m/s2

m = 3 kg

Enrichment

Cartoon owl sitting on a book

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. The same net force acts on two carts. Cart B has twice the mass of cart A. Compared with cart A, cart B's acceleration is…

2. A 10 N net force acts on a 4.0 kg object. What is its acceleration?

3. A net force of 6 N gives an object an acceleration of 2 m/s². What is its mass?

4. For a constant net force, how are mass and acceleration related?

5. Without air resistance, a heavy rock and a light rock fall with the same acceleration. Why?

Force Questions →