2 Another statement of the law

When a resultant force acts on an object it gives the object an acceleration that is directly proportional to the force and inversely proportional to its mass, and in the direction of the force.

• Same mass, greater force → greater acceleration.
• Same force, greater mass → smaller acceleration.

Graph of acceleration against force.

• For a given mass the graph a–F is a straight line through the origin whose slope is 1/m.
• For a smaller mass the slope (and so the acceleration for the same force) is larger.
• For example a 100 kg body has twice the acceleration of a 200 kg body under the same force.