# the effect of forces

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• Created on: 20-12-12 18:19
• The effect of Forces
• weight is the force of gravity acting on the mass of an object
• on Earth's surface, 1kg of mass has a weight of 10N; this is the gravitational field strength (g)
• Newton's first law of motion states that an object at rest stays at rest/ an object in motion stays in motion with the same speed + direction unless acted upon by an unbalanced force
• this can be investigated experimentally e.g. air track + datalogger
• the mass of an object affects how easy or difficult it is to change the movement of that object
• massive bodies have a large amount of inertia, so require a large force to change their motion/ make them move when they're stationary
• the momentum of an object is its mass (kg) multiplied by its velocity (m/s)
• the units of momentum are kg m/s
• Newton's second law of motion states that force = mass x acceleration
• the acceleration of an object is directly proportional to the resultant force and inversely proportional to the object's mass
• in terms of motion, this becomes: force = rate of change in momentum divided by time taken
• when an object falls through the air, first it accelerates + increases in speed because the force of gravity is acting on it
• however,then air resistance (force of friction) increases causing the object to decelerate
• eventually the air resistance force equals the weight of the object and its falling at terminal velocity