Newton's second law states that acceleration is directly proportional to force and inversely proportional to mass. It also specifies that an object accelerates in the direction of the applied force. Force is calculated using the formula F=ma, where F is force in newtons, m is mass in kilograms, and a is acceleration in meters per second squared. Centripetal force is any force directed toward the center of an object's circular path, such as the force exerted by a skater's partner to keep them moving in a circle.

1. Force and mass determine acceleration Newton’s second law Calculate force (F=ma) Force works in a circular motion

2. Newton’s second law The acceleration of an object increases with increased force and decreases with increased mass Small force acceleration larger force acceleration small mass acceleration acceleration larger mass

3. Newton’s second law Also states that the direction in which an object accelerates is the same as the direction of the force force acceleration

4. Calculating force Force= mass x acceleration F= ma Standard unit: newton (N) - The amount of force it takes to accelerate 1 kg of mass 1 m/s 2

5. What force is needed to accelerate a 10 kg shopping cart 3 m/s ? What do you know? m= 10 kg a= 3 m/s What do you want to find out? Force Write the formula: F= ma Substitute the formula: F= 10 kg x 3 m/s Calculate: F= 30 N 2 2 2

6. If a 5 kg ball is accelerating 1.2 m/s what is the force on it? F= ma F= 5 kg x 1.2 m/s F= 6 N A person on a scooter is accelerating 2 m/s . If the person has a mass of 50 kg, how much force is acting on the person? F= ma F= 50 kg x 2 m/s F= 100 N 2 2 2 2

7. Centripetal force Any force that keeps an object moving in a circle Force points towards center of a circle The force that keeps the female skater moving in a circle is the pull exerted by her partner

8. Summary Newton’s second law: Acceleration increases with increased force; decreases with increased mass. An object accelerates in the same direction of the force. F= ma newton (N) Centripetal force: keeps an object going in a circle.