Force and Motion

Unit Review Sheet

Facts and Definitions

Lesson 1: Force and Motion Basics

• A force is a push or a pull.
• Motion is the act of changing position or place.

Lesson 2: Forces

• A contact force (like frictional or applied force) is one that involves objects touching each other. A non-contact force (like magnetism or gravity) does not require objects to touch.
• Forces work in pairs, and many forces can affect an object at the same time. When the forces on an object are unbalanced, they cause the object to move or change direction.
• Normal force is an object pushing back against another object that comes into contact with it.
• Applied force is a force applied to an object by another object.
• Friction or frictional force is a force created by two objects rubbing against each other; it causes moving objects to slow down.
• Tension force is the force transmitted from one object to another through things like string or chain.
• Spring force is created when an object is stretched or compressed and naturally wants to return to its starting position.
• Resisting force or air resistance is a form of friction caused by air pushing against objects.

Lesson 3: Gravity

• Gravity or gravitational force is a non-contact force of attraction between two objects. On Earth, it is felt as a force pushing objects down.
• Mass is the amount of matter in an object.
• Weight is how heavy something feels due to the force of gravity acting on it. While an object's mass is the same everywhere, its weight will be different in space, on other planets, etc.

Lesson 4: Laws of Motion

• Inertia is an object's resistance to changing its motion or state of rest.
• Momentum is the force of an object in motion. The greater the object's mass, the greater its momentum.
• Velocity is the speed of an object in a particular direction; it measures how quickly the position of an object is changing.
• Acceleration is the rate that an object's velocity changes over time.
• The force required to move an object is described by the equation f=ma (force = mass × acceleration).
• Force is measured in newtons (N).
• When forces are balanced, no changes in motion or direction occur. Unbalanced forces occur when one force is stronger than another, and they cause a change in speed or direction.
• Newton's first law (law of inertia) says that an object at rest will remain at rest unless acted upon by an unbalanced force and that an object in motion will remain in motion unless acted upon by an unbalanced force.
• Newton's second law (law of force) says that the acceleration of an object depends on the object's mass and the forces acting upon it. (The greater the mass, the more force needed.)
• Newton's third law (law of action and reaction) says that when an object exerts a force on another object, the second object exerts an equal and opposite force on the first object.

Lesson 5: Magnetism

• Magnetism is a non-contact force that causes magnets to attract or repel each other. The area around a magnet where magnetic force can be felt is called its magnetic field.
• An electromagnet is a magnet whose magnetic field is caused by electric current.

Lesson 6: Buoyancy

• Buoyancy is a force that allows objects to float in a gas or liquid; it is caused by the gas or liquid pushing against the object.
• Volume is a measurement of the amount of space an object occupies.
• Density is an object's mass per unit of volume. It is measured in grams per milliliter (g/mL).
• Displacement occurs when an object is fully or partially submerged in a liquid. The volume of fluid is replaced by the object, and the mass of the water replaced is equal to the mass of the object.
• Pressure is the amount of force that a solid, liquid, or gas exerts on an object by pressing on it. Fluid pressure describes the force of a fluid pushing against an object, while air pressure is the force of air pushing against an object.

Lesson 7: Forces at Work

• A simple machine is a tool or device that makes work easier by changing the direction or strength of a force.
• The six simple machines are lever, wheel and axle, inclined plane, pulley, wedge, and screw.
• Work means using a force to move something.
• Work is measured in joules (J) and shows the amount of force needed to move an object a certain distance.
• The formula is work = force × distance.

Final Project: Force and Motion Stations

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