# Shared Flashcard Set

## Details

physics 115L practical
Embry Riddle Lab Practical questions
25
Physics
11/26/2012

Term
 As the trigger of the spring gun is pulled what is happening to the ball i.e. is it accelerating or not and if so what is causing it to accelerate?
Definition
 The ball is accelerating, and this acceleration is caused by the force being applied to the ball by the spring.
Term
 Once the ball leaves the spring gun is it accelerating and if so what is causing it? (This is tricky THINK about it)
Definition
 Once the ball leaves the spring gun it is accelerating (downward) due to the force of gravity.
Term
 When the ball collides with the pendulum is there a change in momentum? If so explain.
Definition
 Yes there is a change in momentum due to the change in mass caused by the inelastic collision between the ball and the pendulum bob.
Term
 How could we change the system to allow the ball to travel further toward the target?
Definition
 The simplest way to increase the range of the projectile is to increase the angle of the spring gun. This will add a vertical component to the ball’s initial velocity and allow it to travel further. Some slightly more complicated solution would be to decrease the mass of the ball or increase the spring force by increasing the spring constant (k)
Term
 Give me some valid reasons for your shots on target falling short.
Definition
 We were unable to account for any energy loss in the system due to friction, air resistance, vibration, etc.
Term
 At what angle would the acceleration of the cart down the track be equal to (g) and why?
Definition
 A track angle of 90˚ will result in an acceleration equal to (g) this is because the equation for the cart’s acceleration is a ⃗=g ⃗*sin⁡θ and the sine of 90˚ is 1 giving us a ⃗=g ⃗ . This is also quite obvious since a vertical track would lead to a free falling cart.
Term
 Explain the reasons behind the difference between the theoretical acceleration and the measured (experimental) acceleration. Remember that the measured acceleration was either higher or lower than the measured. Give valid reasons for both outcomes.
Definition
 A higher acceleration could be caused by the cart not starting from rest, or by a track angle slightly larger than was measured. A lower acceleration can be caused by friction between the cart and the track, wind resistance or a slight uphill initial velocity.
Term
 During the last part of the experiment (when the cart was pushed up the ramp) there was a clear difference in the look of the three plots (position, velocity, and acceleration) describe these three plots in words and explain why each makes sense. Draw a rough sketch of each if necessary.
Definition
 The plot for position was parabolic starting at a high position (far from the detector, moved close to zero and then back up again. This makes sense because the equation for position (x=x_0+(v_o ) ⃗t+1/2 a ⃗t^2) is quadratic. The plot for velocity had a constant slop, started with high negative values, crossed zero and then continued with to high positive values. This makes sense because the cart was initially pushed up the ramp which would be recorded as negative velocity, as it slowed to a stop under the constant acceleration of gravity the velocity moves across the zero line (the x-axis) and then continues positive. The constant slope is the result of the liner equation for velocity under constant acceleration (v ⃗=(v_0 ) ⃗+a ⃗t). The plot of acceleration is simply a constant (flat) line. This makes sense because the only acceleration acting on the cart in gravity which has a constant value (a ⃗=g ⃗*sin⁡θ=(9.8 m⁄s^2 )*sin⁡θ).
Term
 If we were to increase the angle of the ramp when the cart was midway down, what would change about the shape of the three plots (Position, Velocity, and Acceleration). I expect to see a drawing of each plot similar to what I drew on the board in class.
Definition
 An increase in the angle of the track when the cart was midway down would cause the position plot to suddenly increase its slope. That is, there would be a discontinuity in the quadratic parabola at the moment in time when the ramp angle was increased. The same is true for the velocity plot. At the moment in time when the angle increases the slope of the velocity plot line will also increase. For the acceleration plot we will see a sudden “jump” in the value of the acceleration from a lower value to a higher value.
Term
 What is the point of angling the track? How does it help us? Thank about what it does to the acceleration
Definition
 The point of angling the track allows us to slow the acceleration down slightly. This allows us to make more accurate measurement as everything happens slower.
Term
 List at least two interesting observations you made about friction during the experiment and explain them. I want to know why they are interesting and what you learned from it.
Definition
 One interesting friction observations could be the fact that surface area in contact has no effect on the friction force (shown by putting the block on its side and measuring the same friction force as on its base). A second interesting observation is the difference in friction force between different materials. Though this may seem a bit obvious to sum, it can be quite a surprise to others.
Term
 We know that on a level track we need slightly more mass on the hanger to get the cart moving than the calculations would lead us to believe. Explain to me why this is. I expect to see more than one or two words here
Definition
 This is a result of forces not taken into account during our theoretical calculations acting in the opposite direction to the desired direction of car travel. The most likely candidate for this is of course friction between the cart and the track.
Term
 How does the experiment relate to Newton’s second law? I want to see Newton’s second law in equation form and a good explanation as to how it relates to the experiment.
Definition
 Newton’s second law is given by the equation a ⃗=(∑▒F ⃗ )/m which states that the acceleration experienced by an object is a result of the sum of the forces acting on that object (the mass only adds inertia). Since the purpose of the experiment was to explore the nature of forces acting on objects and see how the acceleration of the objects change with different forces the relation between Newton’s second law and this experiment is very obvious.
Term
 1.       Describe in words the settings and set up of the multimeter when making a measurement of voltage i.e. do you use power? Are you in series or parallel? Etc.
Definition
 To measure voltage you connect the volt meter in parallel with the component you want to measure across. You then turn the power to the circuit on and read the voltage.
Term
 What is the equation for Ohm’s law and what does it mean?
Definition
 The equation for Ohm’s law is: V=I*R this means that as you increase your voltage, for a constant resistance you will get an increase in current etc. This equation is clearly linear meaning that changing any one value will directly affect the others.
Term
 Using Ohm’s Law, calculate the current drawn by a typical electric dryer given a voltage of 240V and a total resistance of 100 ohms.
Definition
 V=I*R Here:V=240V,and R=100Ω ∴240V=I*100Ω Solving for I now gives: I=240V/100Ω ∴I=2.4A
Term
 Design a circuit with an equivalent resistance of 400 ohms given two 200 ohm resistors and one 300 ohm resistors. You must use every resistor and include a diagram.
Definition
 A circuit containing the two 200 ohm resistors in parallel with each other will give you a resistance of 100 ohms, then we simply add in the 300 ohm resistor in series with the parallel 200 ohm resistors and we are there.
Term
 Using the water analogy, give a good description of voltage, current and resistance. If you can come up with a better analogy feel free to use it.
Definition
 Voltage is analogous to the pump in a water line; it’s what is moving the water around the circuit of pipe. Current is analogous to the water itself, more water is analogous to more current. And resistance is analogous to bottlenecks in the pipes or devices that the water does work on, like a milling wheel or an electric generating turbine.
Term
 If a 12 volt potential is applied to a circuit containing two 300 ohm resistors in parallel what is the voltage drop across each resistor?
Definition
 In a parallel circuit the potential drop across each resistor in the parallel branches is the same. Therefore, for a 12V potential applied, we get a 12V voltage drop across each resistor.
Term
 What happens to the current in a parallel circuit containing two resistors of equal resistances? That is how does it DIVIDE through each of the two branches?
Definition
 In a parallel circuit, current divides through the branches according to the resistance in each branch. Therefore, if the total resistance in each branch is the same the current will divide evenly. In other words there will be half the total current moving through each of the two branches.
Term
 Given a complicated circuit containing both series and parallel branches, resistors, light bulbs, and several other components what approach could we use to analyze the circuit? That is list the things we know we can say about the circuit right away, this includes what happens to voltage, and current as it moves through the circuit?
Definition
 Because we know that in a closed circuit (containing no sources or sinks) everything SUMS TO ZERO we can simplify the circuit into sections and analyze each section one at a time. The best approach is to find the total resistance of the circuit and then use that to find the total current draw of the circuit. Once we have that we can analyze the individual branches of the circuit by calculating what percent of the total current will be present in each branch etc.
Term
 True or false: Sound waves are compression waves that produce areas of high and low density in the air.
Definition
 TRUE. Sound waves are NOT longitudinal they are compressional.
Term
 Give one example of an uncommon fluid
Definition
 Glass
Term
 If an aircraft wing produces lift by creating lower pressure on the top of the wing when compared to the underside does that mean that the air is moving faster or slower over the top of the wing?
Definition
 The air moving over the top of the wing of an aircraft is moving FASTER than the air moving beneath the wing. This higher velocity causes a drop in pressure which allows the higher pressure beneath the wing to PUSH the wing skyward.
Term
 If I put my thumb over the end of a garden hose and increase the flow rate have I increased the pressure or lowered it?
Definition
 Increasing the velocity of water flow LOWERS the overall pressure. This is counter intuitive so pay attention.
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