Energy/Forces
If a force causes an object to lose energy, how can we say energy is never created nor destroyed?
The energy was given to the object, and though it may have been converted or transformed, it still exists as part of all of the energy in our world.
What ALWAYS needs to be on a graph?
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Scale
Units
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When would a speed and velocity graph look different?
When an object is going in one direction, then instantly goes a different direction but with the same magnitude.
Explain whether the relationship between force and mass is direct or indirect, and explain how you know this.
F = m x a so as the mass increases, the outcome, or the force, will also increase.
If you are looking at a graph and the y-axis is distance and the x-axis is time, what does the slope of the line represent?
Speed/velocity
Explain why a distance vs time graph that has a perfectly straight, upward, diagonal line would have an acceleration graph who's slope is zero.
If the line is increasing with the same rate between each point, then the rate at which it's velocity/speed is changing is zero.
Why do objects of equal shape but different mass fall at the same rate? Explain why in terms of how gravity is always constant.
If gravity has to be constant in the equation F = m x a, it is only the change in mass that can affect the force due to gravity. This means more mass will have a strong force, able to cause identical motion to an object with a different mass.
If you are looking at a graph of the rate in which distances changes, and the slope is negative, what must this graph represent?
Velocity. rate is change over time, so change of distance over time is either speed or velocity. Only velocity has a direction.
When finding rate, what variable always goes on the x-axis?
Time
Why is it harder to pedal your bike uphill as opposed to down hill? Explain in terms of the sources of the forces.
There is both friction and gravity pushing down on you, so you are exerting a single force against two forces.
When are all of the times the slope of a speed/velocity graph and an acceleration graph both be zero?
When it is moving at a constant speed, or when it is stopped.
Why are velocity, acceleration, and speed different if they are all rates?
They are each a change in something over time, but the variable that is changing is different between each rate. Velocity is magnitude of distance changed, with direction, where as speed is the same but without direction. Acceleration is the change in speed or velocity over time.
Using all of Newton's laws, explain why the cars slowed down on the tracks from our previous lab.
The cars are moving because of the force, due to the acceleration of gravity, acting on it's mass (Law 1). With the force due to gravity pushing in the same direction as the the motion of the car, the force of friction is not a strong enough opposing force to stop it (Law 2). As it flattens out, the force of gravity is no longer at the correct angle to over power the force of friction between the car and the floor, and the forces become equal and opposite (Law 3).
Explain how you would use a graph find the acceleration of an object.
First you would need to find the speed/velocity of the object. When you graph the change in speed/velocity vs the time in which the speed/velocity changes, the slope of that line will be the acceleration.
Why do we use pie charts for PE and KE?
Because the total will always be 100%, but the ratio will change.