Unit 2- Forces consists of Newton's 3 Laws of Motion, different kind of forces and their direction as well as solving problems using different forces.
Newton's First Law: An object at rest will stay at rest and an object in motion will stay in motion until acted on by an unbalanced force. This means that an objects velocity will only changed when an unbalanced force is acting upon it. For example, a skydiver will reach terminal velocity and will fall at a constant speed until something stops it aka the ground.
Newton's second law relates Net force, acceleration and mass stating that F=ma or a=F/m which is stating that acceleration is directly proportional to force but inversely proportional to mass. This is because the unit for force, newtons is derived from kilograms, seconds and meters. An example of this is something that weighs 50 and something weighing 25 kg when acted on by the same force would accelerate at different speeds.
10N= (50kg)a 10N=(25kg)a
a=10N/50kg . a=10N/25
a= 0.2 m/s/s . a= 0.4 m/s/s
Newton's Third Law states that for every force there is an equal and opposite force. These opposing forces however, apply to the two objects that are interacting with each other and not on the same object which is why the object is able to move. These are called force pairs. For example, the Earth exerts a gravitational pull on the moon. Now what most people don't realize is that the moon exerts an equal force back on the earth. This is shown by the tides and while it may not seem as significant as the moon orbiting the earth, it is still equal. The moon just has less mass and therefore can accelerate more due to Newtons 2nd law.
Force can be represented in a couple of different ways being a system schema and force diagrams. System Schemas show how all of the objects interact with each other while a force diagram shows how objects interact with a singular object and it give direction.
https://slabeeber.org/blog/physics_with_adults
This system Schema shows the relationship of a human, a bus, the earth and a handle. The handle is exerting a tension force on the human, the earth is exerting a gravitational force on everything and the human is exerting a Normal force on the bus.
https://physics.stackexchange.com/questions/94835/direction-of-force-of-friction
This diagram is shown at an angle however, a force diagram on needs a point with forces acting upon it represented by vectors. labeling those forces is key such the above diagram with a tension fore, friction, gravity and normal all acting upon the box. Another thing that diagram has shown is the trigonometric equations that are used to solve for different vectors
Solving for different forces and working with them using a force diagram is very similar to working with vectors. To add these vectors you just use the tip to tail method factoring in both direction and magnitude. If the forces are going in opposite directions just subtract the magnitudes. An example of this would be if there was a 150N force going right and a 95N force going to the left then the net force would be 65N going right.
This can be applied to relate force and acceleration using F=ma. Say a 95 kg box has a Friction force of 150N to the left and a Tension force of 650N to the right then what is the acceleration?
Net Force= 650-150
Net Force= 500
a=F/m
a=500N/95kg
a= 5.26 approx.
Solving for different forces and working with them using a force diagram is very similar to working with vectors. To add these vectors you just use the tip to tail method factoring in both direction and magnitude. If the forces are going in opposite directions just subtract the magnitudes. An example of this would be if there was a 150N force going right and a 95N force going to the left then the net force would be 65N going right.
This can be applied to relate force and acceleration using F=ma. Say a 95 kg box has a Friction force of 150N to the left and a Tension force of 650N to the right then what is the acceleration?
Net Force= 650-150
Net Force= 500
a=F/m
a=500N/95kg
a= 5.26 approx.
While this video is a little lengthy it gives an insight on how to solve equations based on force diagrams on an incline as well as making those diagrams based off of a problem.
This video gives a great example of how to use kinematic equations to solve problems with force and motion
This video gives a great example of how to use kinematic equations to solve problems with force and motion
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