Science Quiz Unit 3 PDF

‭Acceleration (and Velocity-time graphs)‬‭, multiple choices, calculate‬ ‭ elocity: the displacement of an object during a time interval divided by the time interval‬ V ‭Acceleration: the change in an object’s velocity in a given amount of time (SI unit: m/s squared)‬ ‭Constant Velocity: An object...

‭Acceleration (and Velocity-time graphs)‬‭, multiple choices, calculate‬ ‭ elocity: the displacement of an object during a time interval divided by the time interval‬ V ‭Acceleration: the change in an object’s velocity in a given amount of time (SI unit: m/s squared)‬ ‭Constant Velocity: An object traveling with uniform motion in a straight line‬ ‭Change in Velocity: The change that occurs when the speed of an object changes, or its direction of‬ ‭motion changes, or both‬ ‭Increasing the stopping time = decreases the acceleration‬ ‭Decreasing the stopping time = increases the acceleration‬ ‭The slope of the velocity-time graph is the average acceleration‬ ‭m/s2‬ ‭Positive slope = positive acceleration (object velocity is increasing in the forward direction)‬ ‭Zero slope = Zero acceleration (object velocity is constant)‬ ‭Negative slope = Negative acceleration (object velocity is decreasing in the forward direction or‬ ‭increasing/speeding up in the backward direction)‬ ‭Equation: a with a hat = v with a hat (change in velocity) / t with a hat (time interval)‬ ‭Aristotle, Galileo Galilei, and Sir Isaac Newton on Motion Ideas‬‭- multiple‬ ‭ ristotle: was curious about how objects would move if there were no outside forces (like gravity) acting‬ A ‭on them‬ ‭-‬ ‭His theories:‬ ‭→ Falling bodies fall at a constant speed.‬ ‭→ Falling bodies fall faster if they are heavier,‬ ‭→ Falling bodies fall slower if they are met by some sort of resistance,‬ ‭→ Every object on Earth has a natural motion or attraction towards the center of Earth (now‬ ‭known as gravitational attraction)‬ ‭→ must apply a force to move an object, keep applying to keep the object moving‬ ‭Galileo: a true “Renaissance thinker”, didn’t agree with Aristotle, disproved his theories, made a U-shaped‬ ‭inclined plane experiment, and wasn’t always correct‬ ‭-‬ ‭His theories:‬ ‭→ Once you stop applying force to an object, friction will slow the object down to a complete‬ ‭stop.‬ ‭→ A body in motion will continue in motion at the same speed unless a force acts on the object‬ ‭from the opposite direction.‬ ‭→ In a vacuum, with all forces of friction removed, all objects fall at the same speed regardless of‬ ‭their mass.‬ ‭→ An object falling freely through the air, or rolling freely down an inclined plane will undergo a‬ ‭constant acceleration.‬ ‭Newton: described acceleration as an imbalance in forces (if there is a force acting on your right side, but‬ ‭there is a stronger force acting on your left side, you will be moved to the right. His first law of motion is‬ ‭still used today, and the characteristic matter to resist changes in motion is called inertia (Newton’s first‬ ‭law of motion = Newton’s law of inertia)‬ ‭Newton's Laws‬‭- calculate, multiple choice, true/false‬ ‭ orce: any influence that alters or causes motion. You exert a force whenever you push or pull an object‬ F ‭(a vector quantity), forces happening in the same direction will strengthen each other, but forces in‬ ‭opposite directions will cancel each other out‬ ‭The first law of motion:‬ ‭-‬ ‭“An object at rest will remain at rest unless acted upon by an unbalanced force. An object in‬ ‭motion will remain in motion in a straight line at a constant velocity unless acted on by an‬ ‭unbalanced force.‬ ‭-‬ ‭Inertia is the tendency of an object to resist change‬ ‭-‬ ‭Formula: Net (total) force = Force A + Force B‬ ‭-‬ ‭Fnet (with a hat) = F A (with a hat) + F B (with a hat)‬ ‭-‬ ‭Newton’s first law only applies to objects moving at a constant speed and when the object is at‬ ‭rest.‬ ‭-‬ ‭The forces acting on an object must be balanced for it to remain at rest (not in uniform motion).‬ ‭The second law of motion‬ ‭-‬ ‭“When a force acts on a mass, acceleration is produced. The greater the mass, the greater the‬ ‭amount of force needed to cause acceleration.‬ ‭-‬ ‭Formula = F (with a hat) = m x a(with a hat)‬ ‭-‬ ‭SI = F = N (newton), m (kg), and acceleration (m/s squared)‬ ‭-‬ ‭Force = the force acting on the object‬ ‭-‬ ‭Mass = how much matter in an object‬ ‭-‬ ‭In a vacuum, all objects fall at the same rate regardless of their mass.‬ ‭Third Law of motion‬ ‭-‬ ‭For every action, there is an equal and opposite reaction.‬ ‭-‬ ‭Action force: The force that initiates the action‬ ‭-‬ ‭Reaction force: The force that responds to the initial reaction‬ ‭-‬ ‭Example 1: You push on a door to open it. (Action: You push on the door, Reaction: The door‬ ‭pushes on you)‬ ‭-‬ ‭Example 2: You throw a baseball to your friend. (Action: Your hand pushes the ball, towards your‬ ‭friend, Reaction: The ball pushes back on your hand.)‬ ‭-‬‭Momentum and Impulse‬ (‭ Don’t worry about direction terminologies)‬ ‭Momentum‬‭- the amount of motion in an object‬ ‭→ the greater the momentum of an object, the more difficult it will be to alter or change that object’s‬ ‭motion‬ ‭→ to bring a moving object to a stop, its momentum must be reduced to 0‬ ‭2 factors to determine momentum‬ ‭1.‬ ‭Velocity: fast moving objects are difficult to stop‬ ‭2.‬ ‭Mass: massive objects are also difficult to stop‬ ‭Formula for momentum: p (with a hat) = m x v (with a hat)‬ ‭SI: kg x m/s‬ ‭-‬ ‭The momentum of an object can change (velocity can change)‬ ‭-‬ ‭Two objects with the same mass might have different momentums, due to differences in velocity‬ ‭-‬ ‭All moving objects have momentum (objects have mass, their moving so they have velocity)‬ ‭-‬ ‭When an object speeds up, it gets momentum‬ ‭-‬ ‭Objects with different masses can have the same momentum when they have different velocities‬ ‭-‬ ‭Direction does matter with momentum, but we don’t consider using words‬  -‭‬ ‭When objects collide, some momentum is lost‬ ‭-‬ ‭A tiny bullet can have more momentum than a big truck if it has a very high velocity‬ ‭Impulse‬‭: the force applied over an interval of time‬ ‭How can you reduce an object’s momentum to zero?‬ ‭1)‬ ‭Apply a force‬ ‭2)‬ ‭Increase the amount of time the force is applied (impulse)‬ ‭Formula: I (with a hat) = F (with a hat) x delta t (time interval)‬ ‭SI: NxS, or just NS‬ ‭-‬ ‭To stop the motion of a vehicle, its braking system applies force on wheels for a long period of‬ ‭time‬ ‭-‬ ‭But in collision, that same impulse is applied for a short amount of time, which can cause forces‬ ‭acting on the car, and damaging occupants‬ ‭-‬ ‭there are devices that use the impulse-momentum relationship to decrease the force applied on‬ ‭cars (air bags, seat belts)‬ ‭-‬ ‭Ex: tossing an egg on the concrete will crack the egg (large force applied for a split second), but‬ ‭we can bring its momentum to zero by throwing the egg into a cushion/mattress, extending the‬ ‭time interval, so the force is much less‬ ‭-‬ ‭First collision: in the example of a car colliding with a building, the impact involves the car and the‬ ‭building. The car’s momentum has been reduced to zero, and the force was very great but applied‬ ‭over a short period of time. Passengers will continue to move forward with the same momentum‬ ‭that the moving car had.‬ ‭-‬ ‭Second collisions: when the passengers of that car hit the steering wheel or other objects that‬ ‭will reduce their momentum to zero (safety devices are now used, such as air bags, seat belts,‬ ‭bumpers, head restaurants, crumple zones, child safety seats, and rollover protective structures)‬ ‭Conservation of Energy‬ ‭ he law of conservation of energy → energy can not be lost or created, but can only be transformed,‬ T ‭converted into different forms of energy, and transferred between objects‬ ‭Ex: In a vehicle collision, energy is transferred from the car to the pavement, into specific areas of the car,‬ ‭and the driver & passengers (and can break them)‬ ‭Different types of energy:‬ ‭-‬ ‭Kinetic energy: the energy of motion‬ ‭-‬ ‭Potential energy: the energy of position with respect to the surface of the Earth (ex: an object‬ ‭falling from two stories up will not fall with as much force or acceleration as an object that falls‬ ‭from 16 floors up)‬ ‭-‬ ‭Heat energy: Energy of molecules in motion (ex: bending and breaking metals and plastics‬ ‭causes them to heat; heat in brakes and tires as they try to stop the vehicle)‬ ‭-‬ ‭Sound energy: the disturbance of molecules‬ ‭Energy can also be stored electrically, chemically, or in elastics and springs.‬ ‭kinetic energy reduced to zero → other forms of energy increases‬ ‭Ex: less motion → more sound and heat‬