Newton’s 2nd Law Notes

Topics What happens when the net force is not ZERO. Newton’s 2 nd Law Relationship between Force, Mass and Acceleration. Solve motion practice problems using Newton’s 2 nd Law.

We Have Already Learned Objects stay in the state of motion they are already at unless they are acted on by an UNBALANCED FORCE. So what happens when objects are acted on by an UNBALANCED FORCE?

When Net Force is NOT ZERO the force is UNBALANCED The object the UNBALANCED Force acts on will ACCELERATE in the direction of the force.

Newton’s 2nd Law is FORCE=MASS x ACCELERATION OR F=ma

F=ma so a= F/m m= F/a

As Force Goes Up Acceleration Goes Up 1kg 2N 4N 1kga=2m/s 2 a=4m/s 2 Force Mass Acceleration Relationships

Force and Acceleration are Directly RelatedThis Means As One Goes Up So Does The Other. As One Goes Down So Does The Other. Force Mass Acceleration Relationships

As Mass Goes Up Acceleration Goes Down 1kg 2 kg 2 N a= 2m/s 2 a= 1m/s 2 Force Mass Acceleration Relationships

Mass and Acceleration Are Inversely Related This means as one goes Up the other goes Down.

Motion Practice Problem If a 10 Newton Force acts on a 5kg Box at what rate will it accelerate? F= 10 N, m=5 kg, a=? F=ma or a = F/m 10N= 5kg x a a= 10N/5kg a=2m/s 2

Practice Problem 2 Acceleration of a 1kg box on a Table Step 1- Label All Forces 10 N 1 kg 20 N Push Force 5 N Friction

Step 2 Find Net Force on x and y axis 5 N 1 kg 20 N 10 N Y axis = 10N-10N= 0N X axis= 20N- 5N = 15N Box will accelerate in the x direction because force is Unbalanced.

Step 3 Calculate Acceleration 1 kg F= ma and a= F/m a= 15N/1kg = 15m/s 2 15 N 15 Newtons is used because that is the Net Force Net Force Diagram