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| Question | Answer |
| What is Force? 1 | forces can’t be seen, but you can see what they do. |
| What is Force? | Force is an interaction that causes a change in motion – they can change speed, direction and shape of things. Described by vectors (represented by arrows) Vectors have magnitude (intensity) and direction Unit of force: Newton |
| Types of Forces | Applied Force Normal Force Magnetic Force Friction Force Electrical Force Gravitational Force |
| Applied Force | Is a force that is applied to an object by a person or another object. Example: If a person is pushing a desk across the room, then there is an applied force acting upon the object. The applied force is the force exerted on the desk by the person. |
| Normal Force | Is the support force exerted upon an object that is in contact with another stable object. Example: if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book. |
| Magnetic Force | Is an attraction or repulsion that happens between electrically charged particles (protons and electrons) because of their motion. It can appear in magnets or electromagnets. |
| Friction Force | It’s the force two materials exert on each other. It’s affected by the type of surface involved, an object’s mass AND how hard surfaces push together. Friction always acts in a direction opposite to the direction of the object’s motion. |
| Gravity Force (Weight) | It’s the attraction force between all matter. It’s affected by the mass of the objects and their distances The force of gravity on an object is called weight Earth: acceleration caused by gravity = 9.8m/s2 Newton realized it is universal (Law of Universal Gravitation) Force: mass x acceleration (F=ma → W=ma) Escape velocity: Earth = 11.2 km/s Moon = 2.5 km/s Jupiter 60 km/s |
| Mass | amount of matter => measure of body’s inertia |
| Weight | effect of gravity on mass Weight = mass x acceleration |
| Balanced | If the forces are balanced: the object is stationary (at rest) the object is moving at a constant speed (unchanging) |
| Unbalanced | When the forces are unbalanced: the object is accelerating the object is decelerating |
| Free Body Diagrams | Free-body diagrams = used to show the relative magnitude and direction of all forces acting upon an object in a given situation. |
| Determining the net force… | Net force: vector sum of all the forces that act upon an object |
| Review: Forces are Balanced | object at rest V = zero m/s objects in motion V ≠ zero m/s a = 0 m/s2 a = 0 m/s2 stay at rest stay in motion (same speed and direction) |
| Contact forces | friction, air resistance, normal force |
| Non-contact forces: | gravity, magnetism, electrical force |
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