Science (oh no)

• A force can cause an object to start moving, speed up, slow down, change direction, or stop. It is also a push or pull exerted on an object.
• The standard unit of force is newton. It is named after Isaac Newton, the scientist who explained how force and motion are related.
• Forces that are equal and opposite in direction are called balanced forces. A book resting on a table demonstrates this.
• In unbalanced forces, one force is greater than the other.
• When two unbalanced forces are exerted in the same direction, the combined force is the sum of the two forces.
• Gravity is the force of one object pulling on another object. Earth pulls all things with this force.
• The law of universal gravitation states that every object in the universe attracts every other object with a gravitational force.
• Weight is the force with which an object is attracted toward another object (e.g., Earth). Mass, on the other hand, is the amount of matter that an object contains.
• A force that requires two objects to touch is called a contact force. One kind of this is friction.
• Friction is the force that results when two objects rub against each other.
• There are four types of friction: static friction, sliding friction, rolling friction, and fluid friction.
• Static friction is the force that prevents an object at rest from sliding in response to the force exerted on it.
• Sliding friction happens when there is a resistive force that opposes the sliding of two solid surfaces over each other.
• Rolling friction is produced when an object rolls over a surface.
• A fluid is a substance that is capable of flowing easily, and changes its shape when acted upon by a force.
• Fluid friction happens when an object moves through a liquid or a gas.
• Fluid friction also occurs when an object falls through the air. This is called air resistance.
• Fluid friction is much less than static or sliding friction. This is why fluids are sometimes used to lessen friction. These fluids are called lubricants.
• When you move from one location to another, you are in motion.
• Galileo Galilei was the first scientist who suggested that once an object is moving, there is no force required to keep that object moving. This knowledge about movement of objects gave Isaac Newton ideas that led him to formulate the three laws of motion.
• Motion is a change in position relative to a frame of reference. Force affects the motion of an object.
• Newton's first law of motion states that an object at rest will remain at rest and an object in motion will stay in uniform motion in the same direction unless a net force acts on it. This is also called as the law of inertia.
• Inertia is a property of matter which is an object's tendency to remain in its state of motion.
• Speed is the ratio between distance and time, it is the distance traveled by a moving object per unit time. Distance is the length between any two points. Time is the period during which a certain distance is covered.
• Another description of motion includes speed and direction. The speed of an object and the direction toward which it is moving comprise the object's velocity.
• Newton's second law of motion describes how acceleration, mass, and force are related. In this law, force is the product of mass and acceleration. It states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
• Newton’s third law of motion states that for every action, there is an equal and opposite reaction. This law is also called the law of action and reaction.
• Acceleration is the rate of change of velocity per unit time. This can also be a decrease in speed. A decrease in speed is called deceleration.
• Energy is the ability to do work.
• A machine is a device or a tool that simplifies work.
• A simple machine is made up of only one or two parts. Some simple machines are often called tools.
• A machine consisting of two or more simple machines is called a compound machine.
• Many machines such as cars, cranes, and clocks have many parts.

  These are called complex machines.
• Work is equal to force into distance. The newton-meter is the metric unit of work.

  One newton-meter is equal to 1 joule. The term joule is used in honor of James Prescott Joule.
• Work done is equal to the amount of energy used when a force moves an object. When doing work, the force used is called the input force. The force that a simple machine exerts in doing work on an object is called the output force.
• There are six kinds of simple machines: lever, pulley, wheel and axle, inclined plane, wedge, and screw.
• A lever is a straight bar that can turn or pivot on a fixed point or support called a fulcrum. All levers have three important parts: load, fulcrum, and effort force. The effort force is the input force the user applies on the lever, while the load is the object on which the force is exerted.
• Energy can be transferred between systems but cannot be created or destroyed.
• The fulcrum in a first-class lever is between the effort force and the load. This lever changes the direction of the force.
• In a second-class lever, the fulcrum is situated at the end close to the load. Force is multiplied in this lever.