Unit 2 Review : Test

This lab was centered on Newton’s Second Law, which is acceleration is directly proportional to force (aka as force increases then acceleration increases, as force decreases then acceleration decreases). Also, acceleration is inversely proportional to mass (aka as mass increases then acceleration decreases, as mass decreases then acceleration increases).

If an object has less mass it is easier to accelerate.

 When an object is going downwards or is being pushed downwards, weight = mass x gravity and gravity is similar to acceleration as in that it’s 10 m/s^2.

In the Newton’s 2^nd Law lab, we had a cart that was accelerating with a hanging weight that was the force of the system – as learned in Newton’s 2^nd Law, acceleration is directly proportional to force. Say if the hanging weight is 3kg and the cart is 2kg. The total mass of the system would be the cart and the hanging weight added together (and anything else added on), which would be 5kg. Use the w=mg to find the net force (Fnet) of the system. Since the hanging weight is the force, you plug in 3 for mass and gravity is 10, so the equation is w=(3)(10); this equals 30 N.
When Skydiving, as speed increases the force of air resistance increases (FAir); thus, speed is directly proportional to air resistance.

F-weight causes you to accelerate, since you’re accelerating you speed up. Every second you continue to go down, your F-weight will always stay the same. To find the Fnet of the skydiver, it is F-weight – FAir = Fnet. The two things that affect Air Resistance is speed surface area (both directly proportional to air resistance). When a diver’s air resistance increases to the amount of the Fweight (they are the same value), then using the equation (since they’re the same amount) the Fnet will be 0m/s^2. In the 1^st unit, Newton’s 1^st law, we learned that when the net force, or acceleration, is 0m/s^2 then the object is at equilibrium, which means the person is at terminal velocity. Another time an object can be at terminal velocity is when it is moving at a constant velocity. This terminal velocity is very fast. When the parachute is opened, the air resistance increases, and since you subtract the air resistance from the weight, the net force becomes negative (aka the acceleration is negative). We learned in the first unit with the hovercraft that when the net force, or acceleration, is negative the object is slowing down. Which is why using a parachute is safe because it slows someone down. However, as they slow down the air resistance beings to decrease, and at that point their air resistance beings to equal their Fweight (terminal velocity); however, now it is at a much slower equilibrium. 
Skydiving and free fall are two different things, but it's easy to confuse the two.
In free fall, the only thing acting upon an object is gravity only. The force due to gravity on a mass is the same as its weight >> w=mg. In the first unit, with constant acceleration, we were able to find how far and how fast an object went with two formulas

Say someone is about to go cliff jumping, and they will hit the water in 3 seconds. You can figure out the height of the cliff by using the "how far" formula >> d= .5 (10)(3^2) >> d= (5)(9) >> d=45m. And with that information you can figure out "how fast" the object was moving >> v=(10)(3) >> v=30m/s. 

If an object is thrown straight up, it will only have a vertical velocity and not a horizontal velocity. If given the time or the velocity, you can figure out the other one needed and also the height. At the top of its path, the object will have a velocity of 0m/s (aka it is not moving). However, you always have to make sure that when the ball is at rest (when you first throw it), the time will always be 0s, or else your data will be completely wrong. 

If an object is throw up at an angle, the only thing that determines the time in the air is the vertical velocity. At the top of its path, the object will still be moving, unlike the object thrown straight up. This is because an object thrown at an angle will always have the same horizontal velocity all throughout its time in the air. With this, there are two special right triangles we will use in class.