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Physics {Forces, Moments, and Momentum Summer} 🚕 - Coggle Diagram
Physics {Forces, Moments, and Momentum Summer} 🚕
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Newton's Laws of Motion
Newton's 2nd Law: An object's acceleration is directly proportional to the resultant force acting upon it, and inversely proportional to the object's mass.
Newton's 3rd Law: Every action has an equal and opposite reaction. This means all forces come in pairs of the same size, but act on objects in the opposite direction.
Newton's 1st Law: An object will not change its motion unless acted on by an unbalanced force. Objects with a greater mass have more inertia so it takes more force to change their motion.
Momentum
Conservation of Momentum the total momentum of a system before an event (collision/explosion) is equal to the total momentum of a system before the event so p is constant
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Change in Momentum force is equal to the change in momentum over time taken. A change in momentum will occur when a force is applied on an object.
Safety Features
All these increase the stopping time before a collision by applying a force for a longer period of time. Since change in momentum= force x time and momentum is constant, as stopping time increases, the force applied on driver decreases, decreasing chance of injury,
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Seatbelts: increases time at which momentum change occurs for driver in a collision, and keeps them in their seat in order to not be thrown out.
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Exam Question: when an object is stationary, and something is thrown
total momentum before = total momentum after as momentum is conserved.
Since the thrower is stationary, the momentum is 0kg m/s.
The force of the throw must be offset to keep the momentum constant so the forward force is combated by the thrower moving backwards.
Centre of Gravity
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for uniform objects, it is the middle of the object
as centre of gravity lowers, the stability of the object increases
Moments
Principle of Moments-For an object to be in equilibrium, the resultant force must be 0 and the clockwise moment= anticlockwise moment.
Moment is the turning effect if the force. A moment occurs when a force applied away from the pivot(turning point) of the object perpendicularly. If distance decreases, force increases.
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Hooke's Law
Elastic Deformation: when objects turn to their original shape after the force has been removed.
Examples: rubber bands, fabrics, steel springs
Inelastic Deformation: when an object remains stretched (does not return to original shape) after force is removed from it.
Examples: plastic, clay, glass
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Hooke's Law states that the amount of force (load) you apply is proportional to the distance it stretches before hitting the limit of proportionality [[elastic limit]].
Graph Since they are directly proportional we can illustrate this relationship in a proportional graph which means a straight line going through the origin.
Investigate how extension varies with applied force for helical spring, metal wires and rubber bands
DORIC: D: extension of spring in cm O:springs R: 3 times I: force applied (masses) C: length of spring with no mass added Prove: Extension is directly proportional to the force applied
Method:
- Set up the clamp and stand and spring like in the picture but first without the masses at the end.
- Measure the length of the spring with a ruler.
- Then add the first mass to the spring.
- Measure the length of the spring again with a ruler.
- Subtract the original length from the new length to find the extension.
- Calculate the force with w=mg by multiplying the mass (kg) by 10.
- Do this with as many masses as you can.
- After that, remove all the masses, and repeat the experiment 3 times to find an average.
Hooke's Law states that the as the force increases, the extension increases up until the limit of proportionality. Plot a graph with the extension of the spring and the force. If there is a straight line passing through the origin, the spring follows Hooke's Law.
Supporting a Beam
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The supports must supply enough upward force to balance the the weight of any object placed on the beam. The pivot is located in the middle of the beam.
The forces must be perpendicular to the pivot. For example, on a horizontal beam, the forces act upwards and downwards respective to the pivot. In this case, the right side of a pivot must qual left side of pivot.