All Flashcards
What is a resistive force?
A force that opposes the motion of an object.
Define terminal velocity.
The maximum speed an object reaches when the constant force (like gravity) and the resistive force balance each other, resulting in zero net acceleration.
What is the time constant ()?
The time it takes for an object to reach approximately 63.2% of its terminal velocity; .
Define in the context of resistive forces.
A positive constant that depends on the shape and size of the object and the properties of the medium (like air density).
What is the mathematical condition for terminal velocity?
, meaning the acceleration is zero.
What are the differences between motion with and without resistive forces?
Without resistive forces: Constant acceleration (often due to gravity), linear change in velocity. | With resistive forces: Acceleration is not constant, velocity approaches a terminal value, exponential change in velocity.
What are the differences between a larger and smaller time constant?
Larger time constant: Object takes longer to reach terminal velocity, either due to larger mass or smaller k. | Smaller time constant: Object reaches terminal velocity more quickly, due to smaller mass or larger k.
What are the differences between the effects of air resistance on a skydiver in a spread-eagle position versus a streamlined dive?
Spread-eagle: Larger surface area, greater air resistance, lower terminal velocity. | Streamlined dive: Smaller surface area, less air resistance, higher terminal velocity.
What are the differences between the motion of a feather and a bowling ball in free fall with air resistance?
Feather: Lower mass, higher surface area to mass ratio, reaches terminal velocity quickly, falls slowly. | Bowling ball: Higher mass, lower surface area to mass ratio, takes longer to reach terminal velocity, falls faster.
What are the differences between initial velocity and terminal velocity?
Initial Velocity: The velocity of an object at the start of its motion, determined by external factors (e.g., how hard it was thrown). | Terminal Velocity: The constant speed that the object eventually reaches when the force of gravity is balanced by the drag force.
What are the general steps to solve for velocity with resistive forces?
- Apply Newton's Second Law ((F_{net} = ma)). 2. Set up the differential equation for velocity. 3. Use separation of variables. 4. Integrate to find the velocity function. 5. Apply initial conditions to solve for constants.
How do you find terminal velocity mathematically?
- Set the net force equal to zero (resistive force + gravitational force = 0). 2. Solve for velocity ((v_t)), which represents terminal velocity.
What happens to velocity, acceleration, and net force as time approaches infinity when an object experiences air resistance?
- Velocity approaches terminal velocity (constant value). 2. Acceleration approaches zero. 3. Net force approaches zero.
What are the steps to determine how quickly an object reaches terminal velocity?
- Calculate the time constant, . 2. A larger mass or smaller k (weaker resistive force) means a longer time to reach terminal speed.
How do you analyze motion with varying resistive forces?
- Draw a free-body diagram to identify all the forces acting on the object. 2. Write out the differential equation and then solve it step-by-step.