1. Chapter 12 Review
Albert’s group

2. Section 1
What Is a Force?
A force can cause a resting object to move, or it can accelerate a moving object by changing the object’s speed or direction
Newtons (N) are the measurement of force
1 N = 1 kg x m/s2

3. Combining Forces
The net force is the overall force acting on an object after all the forces are combined
When the forces on an object are balanced, the net force is zero and there is no change in the object’s motion
When an unbalanced force acts on an object, the object accelerates

4. Friction There are four main types of friction Static friction
The fraction force that acts on objects that are not moving
Sliding friction
The force that opposes the direction of motion of an object as it slides over a surface
Rolling friction
A friction force that acts on a rolling object caused by the change in shape at the point of rolling contact
Fluid friction
A friction force that opposes the motion of an object through a fluid

5. Gravity Gravity is a force that acts between any two masses
Earth’s gravity acts downward toward the center of Earth
Gravity causes objects to accelerate downward, whereas air resistance acts in the direction opposite to the motion and reduces acceleration

6. Section 4 Electromagnetic Forces
Electromagnetic force is associated with charged particles
Electric force and magnetic force are the only forces that can both attract and repel
Electric forces
Act between charged objects or particles such as electrons and protons
Magnetic forces
Act on certain metals, on the poles of magnets, and on moving charges

7. Nuclear Forces
Two forces, the strong nuclear force and the weak nuclear force, act within the nucleus to hold it together
The strong nuclear force is a powerful force of attraction that acts only on the neutrons and protons in the nucleus, holding them together
The weak nuclear force is an attractive force that acts only over a short range

8. Gravitational Force
Gravitational force is an attractive force that acts between any two masses
Newton’s law of universal gravitation states that every object in the universe attracts every other object
Centripetal force is a center-directed force that continuously changes the direction of an object to make it move around the center