P4 - Explaining Motion

• Friction - The force that opposes the motion of two surfaces that are in contact with each other.
• Gravitational Field Strength - The size of gravitational attraction per unit mass
• Mass - Amount of matter
• Weight - Force of gravitational attraction on a mass
• Normal Contact Force - Force exerted by a hand surface on an object that presses on it
• Interaction pairs (Newtons 3rd law) - For every action, there is an opposite and equal reaction. If there are 2 object involved - the forces act in pairs. The forces are equal in size but opposite in direction
• Acceleration = Change in speed/Time
• (Final Speed)^2 - (Initial Speed)^2 = 2 x Acceleration x Distance
• Velocity is the rate of change of displacement, measured in metres per second (m/s). It is a vector quantity, unlike speed.
• Speed is the rate of change of position in a given time period. It is measured in metres per second (m/s). It is a scalar quantity.
• Displacement is the shortest distance between two points. It is measured in meters.
• The average velocity of an object over a certain interval of time is calculated as the ratio of the displacement to the elapsed time. Average Velocity = Displacement / Time Taken
• Momentum is a measure of how difficult it is to stop a moving object
• The higher the momentum, the more difficult it is to stop a moving object
• Momentum = Mass x Speed
• Change in momentum = Force x Time
• The conservation of momentum is the principle that the total momentum is the same before and after the collision
• Gravitational potential energy is the energy stored when two interacting objectd are moved apart
• Gravitational Potential Energy = Height x mass x gravitational field strength
• Kinetic energy is the energy stored in an object has because of its motion
• Kinetic energy = 1/2 x mass x speed^2
• Work done is the amount of energy transferred whenever a force makes something move
• Speed-time graphs show the speed journey of an object. The area under the graph shows the distance travelled
• Velocity-time graphs show velocity as a function of time. Gradient at any point gives acceleration, area under the curve gives displacement
• Acceleration-time graphs show how acceleration changes over time. Area under the curve gives displacement, gradient at any point gives acceleration
• Distance-time graphs show distance covered by an object against time. Slope at any point gives average speed, area under the curve gives total distance travelled
• Average Velocity = Total Distance / Time taken to travel that distance