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Newton's Second Law states that the acceleration of an object is directly proportional to the resultant force in its direction as the force and is inversely proportional to the mass of the object. It can be expressed using the following formula: Resultant Force = mass × acceleration. This equation can only be used when the acceleration of the moving object is constant.
Acceleration is the rate of change of velocity of an object. It is a vector quantity, as it is expressed by both magnitude and direction. It can be calculated using the following equation: acceleration = change in velocity/time.
Deceleration is negative acceleration. It is calculated using the same equation as acceleration. A positive deceleration is a negative acceleration, ie. an object which is slowing down.
A velocity-time graph is a graphical representation of an object's motion over a given period of time. The direction and the speed of an object can be deduced from the velocity-time graph of its motion. The area under the velocity-time graph of an object's motion gives its displacement.
The gradient of a velocity-time graph gives the acceleration of an object. A positive gradient shows that the object is accelerating, whereas a negative one shows that it is decelerating.
Objects with mass have a gravitational field around them and thus they experience a pulling force. This is the force caused by gravity. The Earth's gravitational field strength is 10 m/s², and thus for every kg of mass of an object, it experiences a force of 10 N caused by gravity. When objects are falling near the surface of the Earth, the Earth's gravitiational field exerts a pulling force on the object. This causes a resultant force to act on the object, and thus, by Newton's Second Law, the falling object accelerates towards the surface of the Earth due to gravity. This force is also called the weight and it can be calculated using the following formula: Weight = mass × gravitational field strength.
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