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Questions and Answers
What is the SI unit used to measure force?
What is the SI unit used to measure force?
- Pascal (Pa)
- Meter (m)
- Newton (N) (correct)
- Kilogram (kg)
How is weight determined for an object on Earth?
How is weight determined for an object on Earth?
- By using the formula $W = F/m$ where $F$ is the frictional force.
- By using the formula $W = mg$ where $g$ is the speed of light.
- By calculating the mass and multiplying by gravitational potential energy.
- By using the formula $W = mg$ where $g$ is the acceleration of free fall. (correct)
What type of force is friction?
What type of force is friction?
- A gravitational force acting on an object.
- A force acting in the same direction as the motion.
- An upward buoyancy force in a fluid.
- A force that arises when two surfaces rub against each other. (correct)
What does the formula $F = ma$ represent?
What does the formula $F = ma$ represent?
Which of the following correctly describes free-body diagrams?
Which of the following correctly describes free-body diagrams?
In a fluid, what is the buoyant force acting upon an object called?
In a fluid, what is the buoyant force acting upon an object called?
If a force results in constant acceleration, what must be true about the force acting on the object?
If a force results in constant acceleration, what must be true about the force acting on the object?
What effect does changing the location of an object (e.g., from Earth to the moon) have on its weight?
What effect does changing the location of an object (e.g., from Earth to the moon) have on its weight?
What forces act on an object on a slope?
What forces act on an object on a slope?
How is drag force related to the speed of an object?
How is drag force related to the speed of an object?
What happens to an object in free fall once it reaches terminal velocity?
What happens to an object in free fall once it reaches terminal velocity?
Which factor does NOT significantly influence the magnitude of drag force?
Which factor does NOT significantly influence the magnitude of drag force?
What is the effect of increasing the cross-sectional area of a falling object in fluid?
What is the effect of increasing the cross-sectional area of a falling object in fluid?
In which scenario will an object's acceleration reduce to zero?
In which scenario will an object's acceleration reduce to zero?
Which statement about terminal velocity is false?
Which statement about terminal velocity is false?
How can terminal velocity be experimentally determined for an object?
How can terminal velocity be experimentally determined for an object?
What is the unit of pressure that measures force per unit area?
What is the unit of pressure that measures force per unit area?
Using the formula $p = h \rho g$, what does the variable $h$ represent?
Using the formula $p = h \rho g$, what does the variable $h$ represent?
According to Archimedes' principle, what condition must be true for an object to float?
According to Archimedes' principle, what condition must be true for an object to float?
What forces act on an object submerged in a fluid?
What forces act on an object submerged in a fluid?
Why does pressure at the base of a column of fluid remain uniform in all directions?
Why does pressure at the base of a column of fluid remain uniform in all directions?
What is the significance of the centre of mass in relation to motion?
What is the significance of the centre of mass in relation to motion?
Which method can be used to find the volume of an irregular solid?
Which method can be used to find the volume of an irregular solid?
For a body to be in equilibrium, what must be true about the net forces acting upon it?
For a body to be in equilibrium, what must be true about the net forces acting upon it?
What does the equation for pressure represent?
What does the equation for pressure represent?
How can the centre of mass of an object be determined using a plumb line?
How can the centre of mass of an object be determined using a plumb line?
In the context of equilibrium, what is a triangle of forces used for?
In the context of equilibrium, what is a triangle of forces used for?
What is the SI unit of density?
What is the SI unit of density?
What is the formula to calculate density?
What is the formula to calculate density?
What must be true about the motion of a ball bearing once it reaches terminal velocity in a fluid?
What must be true about the motion of a ball bearing once it reaches terminal velocity in a fluid?
How is the moment of a force defined?
How is the moment of a force defined?
What is a couple in the context of rotational forces?
What is a couple in the context of rotational forces?
What condition defines a body in equilibrium regarding moments?
What condition defines a body in equilibrium regarding moments?
What is the SI unit for measuring the moment of a force?
What is the SI unit for measuring the moment of a force?
What happens if a force is applied parallel to the pivot?
What happens if a force is applied parallel to the pivot?
How can the torque of a couple be calculated?
How can the torque of a couple be calculated?
Which statement is true about terminal velocity?
Which statement is true about terminal velocity?
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Study Notes
Dynamics
- Force: A resultant force acting on a body with mass causes acceleration.
- Force formula: F = ma (Force = mass × acceleration)
- Newton: The SI unit of force, defined as the force that accelerates 1 kg by 1 m/s².
- Weight: The gravitational force acting on an object, calculated as W = mg (Weight = mass × acceleration due to gravity).
Common Forces
- Weight: The gravitational force acting on an object through its center of mass.
- Friction: Resistive force arising when two surfaces rub against each other.
- Drag: Resistive force on an object moving through a fluid (e.g., air or water).
- Tension: Force within a stretched cable or rope.
- Upthrust: Upward buoyancy force acting on an object in a fluid.
- Normal Contact Force: Force acting at 90° to the plane when an object rests against another.
Free-Body Diagrams
- Model forces acting on an object with vector arrows scaled to their magnitudes and directions.
- Label each arrow with the force it represents.
- Used to identify forces in planes and resolve net force in a specific direction.
Motion under Constant Force
- Constant net force results in constant acceleration (F = ma).
- Applies to motion on slopes, where forces are resolved parallel and perpendicular to the slope.
Non-Uniform Acceleration: Drag
- Drag is a frictional force opposing motion through a fluid (air resistance).
- Factors influencing drag include:
- Speed of the object.
- Object's shape and texture.
- Fluid density.
- Drag increases with the square of speed and cross-sectional area.
Terminal Velocity
- Drag force increases with velocity during free fall, reducing net force and acceleration.
- Terminal velocity is reached when drag force equals weight, resulting in zero net force and constant velocity.
Determining Terminal Velocity
- Experimentally:
- Drop a ball bearing in viscous fluid, measuring the distance traveled at equal time intervals.
- Use a ticker timer to mark a tape attached to the ball bearing, analyzing dot spacing.
- Measure the distance traveled between dots, determine terminal velocity using time interval.
Equilibrium
- Moment of a force: The turning effect of a force around a pivot point, M = Fd (Moment = Force × perpendicular distance).
- Couple: A pair of equal magnitude, opposite direction forces acting in parallel, producing rotation without translation.
- Torque: Product of one force's magnitude and perpendicular distance between forces, equaling the total moment of the couple.
Principle of Moments
- In equilibrium:
- Net force is zero.
- Net moment is zero.
- Sum of clockwise moments equals the sum of anti-clockwise moments about the same point.
Center of Mass and Center of Gravity
- Center of mass: The point where an object's weight appears to act.
- Center of gravity: Coincides with center of mass when the object is in a uniform gravitational field.
- A freely suspended object comes to rest with its center of mass below the suspension point.
Density and Pressure
- Density: Mass per unit volume, ρ = m/V (Density = mass / volume).
- Pressure: Force per unit area, p = F/A (Pressure = force / area).
- Pressure in a fluid: p = hρg (Pressure = height of fluid column × density × acceleration due to gravity).
Archimedes' Principle
- Upthrust: Upward force acting on an object submerged in a fluid.
- Archimedes' Principle states that the upthrust on an object is equal to the weight of the fluid displaced by the object.
- An object sinks if upthrust is less than its weight.
- A floating object has its weight equal to the weight of the fluid it displaces.
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