Newton's Second Law relates force, mass, and acceleration using the equation F=ma. The equation can be rearranged to solve for force. Force is measured in Newtons, where 1 Newton is the force needed to accelerate a 1 kilogram mass at 1 meter per second squared. If acceleration is held constant and an object's mass doubles, the force needs to double to maintain the same acceleration according to the Second Law.

2. Newton ’s Second Law can be expressed with an equation: Which can be re-arranged to isolate Force like this:

3. Force is measured in Newtons A Newton = the amount of force needed to accelerate a 1 kilogram mass at a rate of 1 m/s 2 Since F = m . a 1 N = 1 kg . m/s 2

4. 1. Describe the motion of the object this graph depicts 2. Using F = ma, calculate the mass of the object

5. Describe the motion of the object this graph depicts the object is accelerating 2. Using F = ma, calculate the mass of the object using rise/run: 3N-1N/3m/s 2 – 1m/s 2 = 1 kg

6. If there is acceleration (speed up, slow down, change direction), there is an unbalanced force. remember: another name for unbalanced force is net force

7. Look at the relationship between force, mass, and acceleration in this equation: To keep the same acceleration, what must force do if mass is increased? force must increase just as much

8. To be more specific: If acceleration stays constant and the mass of the object doubles, what must the force be doing? doubling

9. We already know that the formula for the second law of motion is F = ma We can use this formula to calculate the force of weight Weight = mass x acceleration gravity

10. It ’s really, really important to remember: a net force results in acceleration no net force does not mean no motion – an object can move at a constant speed in a straight line with no net force!!! – IF it was already in motion.

11. The force required to accelerate a 2 kg mass at 4 m/s 2 is (a) 6N (b) 2N (c) 8N (d) 16N Answer The correct answer is 8N because F = ma and so F = (2 kg)(4 m/s 2 )

12. What force will be needed to accelerate a 8kg mass at the same acceleration as a 4kg mass? (a) the amount of force does not change (b) the force needs to be 4x ’s as much (c) the force should double (d) it will take half as much force Answer The correct answer is “the force should double” because the mass doubled while acceleration was held constant.

13. A cart has a constant acceleration from rest. The force on the cart must be (a) decreasing (b) zero (c) constant (d) increasing Answer The correct answer is “constant” because a constant net force creates a constant acceleration.