HFS Flashcards
What is a projectile?
Any object thrown into space upon which the only acting force is gravity
How are time and distance resolved from a projectile fired with no angle?
- Calculate the time the projectile would take to hit the ground if it were dropped using sqrt(2s/a).
- This time is equal to the fired projectile as the horizontal component of an object’s velocity is independent to the vertical component of its velocity
- Use d = st to calculate total distance or s = vt to calculate total displacement
How are time and distance calculated from a projectile fired at an angle to the horizontal level from the ground?
- Resolve the horizontal and vertical vectors for the initial velocity of the object using a vector triangle
- Calculate the time taken to reach the maximum vertical displacement using
- Calculate maximum height using (v^2 - u^2)/2g
- Calculate total time that the object is in the air for using t = √(2h/g)
- Calculate horizontal distance using s = vt, multiplying the horizontal vector by the total time
How are time and distance calculated from a projectile fired at an angle above or below the horizontal?
What is Newton’s First Law?
An object will remain stationary or will continue to travel at a constant velocity until external forces act upon it.
What is Newton’s Second Law?
F = ma
What is Newton’s Third Law?
If Object A exerts a force on Object B, Object B will exert a force on Object A which is equal in magnitude and opposite in direction.
State the equipment used when determining the acceleration of a falling object.
CPAC 1
- Clamp stand
- Clamp
- Light gate (P)
- Picket gate (P)
- Data logger (C)
- Electronic timer (C)
- Ball bearing (C)
- Metre rule (C)
- Ruler (P)
- Metal
clamp/electromagnet opened/activated by a button (C) - Insulated wires
- Pressure plate (C)
‘C’ denotes that the piece of apparatus is used for the circuit method.
‘P’ denotes that the piece of apparatus is used for the picket gate method.
State the equations used when determining the acceleration of a falling object.
CPAC 1
v = s/t
v = s/t^2
Describe the circuit method used when determining the acceleration of a falling object.
CPAC 1
- Attach a metal clamp/electromagnet which is opened/deactivated by a button to a clamp stand. Connect the appliance used to an electronic timer, placing the ball bearing in the clamp/on the electromagnet. Connect the pressure plate to the electronic timer.
- Release the ball bearing using the button, starting the timer.
- The ball bearing will fall downwards, landing on the pressure plate which stops the timer.
- Record the time taken for the ball bearing to fall from the clamp/electromagnet to the pressure plate.
- Reset the electronic timer.
- Repeat steps 2-5 two to four more times.
- Measure the difference from the starting position of the ball bearing (in the metal clamp/electromagnet) to the final position of the ball bearing (the pressure plate) using a metre rule. Record the value in metres.
- Calculate the mean time taken for the ball to travel from the clamp/electromagnet to the pressure plate by dividing the sum of all non-anomalous values by the number of non-anomalous values.
- Use the equation v = s/t to calculate the mean velocity of the ball bearing.
- Use the equation a = 2s/t^2 - ut to calculate mean acceleration due to freefall (g).
Describe the picket gate method used when determining the acceleration of a falling object.
CPAC 1
- Attach a light gate to a clamp stand using a clamp. Using insulated wires, connect it to a data logger.
- Measure and record the length of opaque and transparent intervals on the picket gate using a ruler.
- Drop the picket gate through the light gate, ensuring that it does not touch the light gate, clamp, etc while it is falling, and that it is caught or lands on a soft surface.
- Record data (time, distance travelled, velocity and acceleration) from the data logger.
- Repeat steps 2-4 two to four more times.
- Select the most consistent set of results. Plot velocity against time on a graph, drawing a linear line of best fit.
- Acceleration due to freefall (g) is equal to the gradient of the line plotted. Calculate this by dividing the change in velocity by the change in time.
State the potential sources of error when determining the acceleration of a falling object.
CPAC 1
- Pressing the button started the timer sometimes
- Sometimes activating the pressure plate would not stop the timer, potentially leading to estimation from memory and inspection.
- Incorrect setup
- Malfunctioning electronic timer
- Misreading value from electronic timer
- Incorrectly measured falling distance
State the dependent and controlled variables when determining the acceleration of a falling object.
CPAC 1
The dependent variable is time (taken for the ball to fall a known distance).
Controlled variables in this investigation include:
- Density of the medium (air)
- Temperature (room temperature, do not open windows or turn on heaters during the investigation)
- Surface area of ball (use the same ball)
- Distance fallen by ball bearing
- Person dropping picket gate
State the potential hazards and risks when determining the acceleration of a falling object.
CPAC 1
Hazards:
- Electrical devices
- Picket gate
- Ball bearing
Risks:
- Electric shock
- Shattering of picket gate
- Choking
Define a force couple.
Two forces which are equal in magnitude and opposite in direction. Their lines of action do not coincide, producing a turning effect.
