Force and Newton’s 2 nd Law

What is Force?  Definition:  A push or pull acting on an object  The SI unit for force is the Newton (N)  1 Newton is the force required to cause a mass of 1 kg to accelerate at 1 m/s 2  Examples:  Gravity  Friction  Applied force  Definition:  A push or pull acting on an object  The SI unit for force is the Newton (N)  1 Newton is the force required to cause a mass of 1 kg to accelerate at 1 m/s 2  Examples:  Gravity  Friction  Applied force

How is Force related to Motion?  Forces cause all motions  Every time the motion of an object changes, it’s because a force has been applied to it  Forces can cause stationary objects to start moving or a moving object to change its speed, direction, or both  What is it called when something changes speed or direction?  Forces cause all motions  Every time the motion of an object changes, it’s because a force has been applied to it  Forces can cause stationary objects to start moving or a moving object to change its speed, direction, or both  What is it called when something changes speed or direction?

How does Force affect Acceleration?  Amount of acceleration depends on 2 variables:  Strength of the force applied  Mass of the object  If you know Force and Mass you can calculate Acceleration  Acceleration equals force divided by mass  a = F/m  Amount of acceleration depends on 2 variables:  Strength of the force applied  Mass of the object  If you know Force and Mass you can calculate Acceleration  Acceleration equals force divided by mass  a = F/m

Newton’s Second Law  Describes the equation used to calculate acceleration from force and mass  Newton’s Second Law:  The acceleration of an object equals the net force acting on the object divided by the object’s mass  Describes the equation used to calculate acceleration from force and mass  Newton’s Second Law:  The acceleration of an object equals the net force acting on the object divided by the object’s mass

Who is Issac Newton?  English physicist who lived in the 1700’s  Developed 3 laws of motion and the law of gravity  English physicist who lived in the 1700’s  Developed 3 laws of motion and the law of gravity

Force and Acceleration Practice  With what fore will a car hit a tree if the car has a mass of 3,000 kg and it is accelerating at a rate of 2m/s 2  A 10 kg bowling ball would require what force to accelerate it down an alleyway at a rate of 3 m/s 2  With what fore will a car hit a tree if the car has a mass of 3,000 kg and it is accelerating at a rate of 2m/s 2  A 10 kg bowling ball would require what force to accelerate it down an alleyway at a rate of 3 m/s 2  What is the mass of a falling rock if it hits the ground with a force of 147 newtons?  What is the acceleration of a softball it if has a mass of 0.50 kg and hits the catcher/s glove with a force of 25 newtons?