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Forces & Motion

Science, Grade 7

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US A Gravity & Motion Gravity is a type of force that pulls objects toward each other and toward the Earth. The amount of gravitational force depends upon the mass of the objects and the distance between them. The acceleration of an object near the surface of the Earth due to gravity is 9.8 m/s2. If both the acorn and leaf fall from the tree at the same time, air resistance will slow down the leaf and the acorn will hit the ground first. In a vacuum, both will reach the ground at the same time. Newton’s Law of Gravitation All objects in the universe apply a gravitational force (force of attraction) on other objects. The strength of the gravitational force is dependent upon the mass of the objects and the distance between them. The larger the mass of the objects, the larger the force is between the two objects. The farther away the two objects are, the weaker the gravitational force is between them. larger mass larger force similar size similar force larger distance weaker force gravity vacuum air resistance gravity Momentum acceleration acceleration acceleration acceleration What Is Force? Scientists define force as a push or a pull. A force is described by its strength and direction in which it exerts. A force provides an object with the energy to move, stop moving, or change direction. Newton (N) is the standard unit of measure for force. Newton’s Laws of Motion The scientist we usually think of when we talk about gravity and falling objects is Isaac Newton. Newton is credited with the development of three laws dealing with the movement of objects. Newton’s First Law of Motion An object at rest tends to stay at rest and an object in motion tends to stay in motion at the same speed and in the same direction unless a force acts on it. When the same force is applied to both carts, the acceleration of the empty cart will be greater than the acceleration of the loaded cart. Newton’s Third Law of Motion For every action there is an equal and opposite reaction. The amount of motion that takes place is momentum. To calculate momentum you multiply the mass of an object by its velocity. The momentum and velocity of an object are always in the same direction. When groups of objects are involved, if there is no outside force, the total momentum of the group does not change. For example, in a collision between two cars, momentum may be transferred from one car to the other but not lost. This is referred to as the Law of Conservation of Momentum. Newton’s Second Law of Motion Acceleration is produced when a force acts on an object. Acceleration of an object depends on its mass and the amount of force applied. The relationship of acceleration (a) to mass (m) and force (F) can be expressed in mathematical terms as follows: M x V = Momentum object at rest object in motion © Copyright NewPath Learning. All Rights Reserved. 94-4802 www.newpathlearning.com Forces & Motion

Key Vocabulary Terms • acceleration • force • gravitational force • gravity • mass • momentum • motion • Newton (N) • speed • velocity \|xiBAHBDy01803sz\ When the same force is applied to both carts, the acceleration of the empty cart will be greater than the acceleration of the loaded cart. acceleration acceleration acceleration acceleration USA What Is Force? _____________________________ _____________________________ _____________________________ _____________________________ _____________________________ _____________________________ Gravity & Motion Define gravity: _______________________________ _______________________________ _______________________________ _______________________________ _______________________________ The acceleration of an object near the surface of the Earth due to gravity is 9.8 m/s2. If both the acorn and leaf fall from the tree at the same time, air resistance will slow down the leaf and the acorn will hit the ground first. In a vacuum, both will reach the ground at the same time Newton’s Laws of Motion Who is Isaac Newton? _______________________________________ __________________________________________________________ Newton’s First Law of Motion __________________________________________________________ __________________________________________________________ a = or F = x Newton’s Law of Gravitation ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________ Newton’s Third Law of Motion __________________________ __________________________ __________________________ ________________________ Momentum The amount of motion that takes place is ____________________. To calculate momentum you multiply the ______________ of an object by its _________________. The momentum and velocity of an object are always in the same direction. When groups of objects are involved, if there is no outside force, the total momentum of the group does not change. For example, in a collision between two cars, momentum may be transferred from one car to the other but not lost. This is referred to as the ___________________________________. Newton’s Second Law of Motion __________________________________________________________ __________________________________________________________ __________________________________________________________ The relationship of acceleration (a) to mass (m) and force (F) can be expressed in mathematical terms as follows: x = Momentum ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ ___________________________ object at rest object in motion © Copyright NewPath Learning. All Rights Reserved. 94-4802 www.newpathlearning.com Forces & Motion gravity vacuum air resistance gravity

Forces & Motion

Science, Grade 7

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