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Physics OAT 2-3-4
| Question | Answer |
|---|---|
| What is kinematics? | The science of describing the motion of objects, including position, displacement, velocity, and acceleration — without considering the forces causing the motion. |
| What is displacement, and is it a scalar or vector? | Displacement is the change in position (Δx = x_f − x₀). It is a vector — it has both magnitude and direction, and can be positive or negative. |
| What is distance, and is it a scalar or vector? | Distance is the total length traveled along a path. It is a scalar — magnitude only, always positive. Calculated by adding up each leg of the journey. |
| What is acceleration? | The rate of change of velocity: a = Δv / Δt. It is a vector quantity with units of m/s². It can represent speeding up, slowing down, or changing direction. |
| If acceleration and velocity point in the same direction, what happens? | The object speeds up. |
| If acceleration and velocity point in opposite directions, what happens? | The object slows down. |
| What does the slope of a position vs. time graph represent? | Velocity (m/s). Rise over run = Δposition / Δtime. |
| What does the slope of a velocity vs. time graph represent? | Acceleration (m/s²). Rise over run = Δvelocity / Δtime. |
| What is free fall? | Motion where gravity is the only force acting on an object (air resistance ignored). All objects accelerate downward at g = −9.81 m/s² (use −10 m/s² on the OAT). |
| What is the acceleration of a ball at its highest point during free fall? | Still −10 m/s² (gravity is constant throughout the entire flight). Only the velocity is zero at that moment, not the acceleration. |
| What is projectile motion? | Motion of an object launched into the air, with constant velocity horizontally and constant downward acceleration (gravity) vertically. Air resistance is ignored. |
| How do you find the x and y components of initial velocity? | v_iy = v_i · sin(θ) — vertical component v_ix = v_i · cos(θ) — horizontal component |
| What are the side ratios of the two special triangles to memorize? | 45-45-90: sides are 1, 1, √2 30-60-90: sides are 1, √3, 2 (hypothenuse is 2, bottom length is √3). Opposite of 60 is √3, opp of 30 is 1. |
| What is the key difference between constant velocity and constant acceleration? | Constant velocity: no change in speed or direction. Constant acceleration: speed and/or direction continuously changes. |
| A dropped object starts from rest. What kinematic equation simplifies the free fall distance? | Since v_i = 0, equation 1 simplifies to: Δy = ½·g·t². The direction is negative if you define downward as negative. |
| In a position vs. time graph, what does a curved (non-linear) line indicate? | The object is accelerating — velocity is changing over time. A straight line indicates constant velocity (zero acceleration). |
| What is the sign convention typically used in free fall and projectile problems? | Upward is positive, downward is negative. So g = −10 m/s² when used in equations. |
| What is dynamics, and how does it differ from kinematics? | Dynamics studies the forces that cause objects to move, while kinematics only describes the motion itself. Dynamics asks "why" an object moves; kinematics asks "how" it moves. |
| What is Newton's First Law (Law of Inertia)? | An object at rest stays at rest, and an object in motion stays in motion at constant speed and direction, unless acted upon by a net external force. |
| What is inertia, and what does it depend on? | Inertia is an object's resistance to changing its state of motion. It is directly proportional to mass — the greater the mass, the greater the inertia. |
| What is Newton's Second Law, and what is its formula? | The acceleration of an object is directly proportional to the net force and inversely proportional to its mass. Formula: F = ma, where F is in Newtons (N), m in kg, and a in m/s². |
| What is Newton's Third Law? | For every action, there is an equal and opposite reaction. When object A exerts a force on object B, object B exerts a force of equal magnitude but opposite direction on object A. These force pairs always act on different objects. |
| What is the difference between mass and weight? | Mass is the amount of matter in an object (kg) and does not change with location. Weight is the gravitational force on an object (N) and changes depending on the gravitational field. W = mg. |
| What is the normal force, and in what direction does it act? | The normal force is the force a surface exerts to support an object resting on it. It always acts perpendicular (at a right angle) to the contact surface, opposing gravity. |
| What are the two key equations for solving dynamics problems? | F_net = ΣF (sum of all forces in a given direction) F_net = ma |
| On an inclined plane, what are the x and y components of gravity? | Fg,x (along the slope) = mg·sin(θ) — pulls the object down the slope Fg,y (perpendicular to slope) = mg·cos(θ) — pushes into the surface |
| What is static friction, and when does it apply? | Static friction opposes forces on an object that is at rest, preventing it from starting to move. It can vary up to a maximum value: F_f(static) ≤ μs·F_N. |
| What is kinetic friction, and when does it apply? | Kinetic (dynamic) friction opposes the motion of an object that is already moving. It is constant and generally less than maximum static friction: F_f(kinetic) = μk·F_N. |
| How do you determine if an object on a slope will move? | Calculate the gravitational force along the slope (mg·sin θ) and the maximum static friction (μs·F_N). If mg·sin θ exceeds F_f(static), the object moves. If not, it remains at rest. |
| What is tension, and in what direction does it always act? | Tension is a pulling force transmitted through a rope or cable. It always pulls — it can never push. When a rope is at an angle, its tension must be broken into x and y components. |
| How do you find the net force when forces act in both x and y directions? | Find the x and y components separately, then use the Pythagorean theorem: F_net = √(F_netx² + F_nety²). Use tangent to find the angle: θ = tan⁻¹(F_nety / F_netx). |
| What is apparent weight, and how does elevator acceleration affect it? | Apparent weight is the normal force a scale reads — not true weight. If an elevator accelerates upward, app weight increases. If it accelerates downward, app weight decreases. If stationary or at constant velocity, apparent weight equals true weight. |
| What is the step-by-step strategy for solving any dynamics problem? | Draw a free-body diagram and label all forces. Set the x-axis parallel to the direction of motion. Break all forces into x and y components. Apply ΣF = ma separately in each direction. Solve for the unknown. |
| What is statics? | A subdivision of dynamics dealing with objects in equilibrium, where net force and net torque both equal zero. |
| What are the two types of equilibrium? | Static equilibrium (object at rest) and dynamic equilibrium (object moving at constant velocity). In both cases, net force and net torque = 0. |
| What is stable equilibrium? | When displaced, the object returns to its original position. The center of gravity (cg) remains within the base of support. |
| What is unstable equilibrium? | When displaced, the object does not return to its original position. The cg moves outside the base of support. |
| What is neutral equilibrium? | When displaced, the object remains in its new position (e.g., a ball on a flat surface). |
| What is the critical point? | The moment when the cg is no longer directly above the base of support — causing the object to tip over. |
| How can a human increase stability? | Lower the cg (bend knees) or widen the base of support (wider stance or using a cane). |
| What is torque? | A rotational force applied at a point other than the axis of rotation. Formula: τ = rF sinθ, measured in Newton-meters (Nm). |
| What is the axis of rotation? | The fixed point about which an object rotates. Forces applied at the axis cause translation; forces elsewhere cause rotation. |
| What are the two equilibrium conditions used in statics problems? | Net force = 0: ΣF = 0 Net torque = 0: Στ clockwise = Στ counterclockwise |
| In a dynamic equilibrium friction problem, what must be true about net force? | Net force = 0 in both x and y directions, so friction force equals the horizontal component of tension, and normal force accounts for the vertical tension component. |
| What is the center of gravity (cg)? | The average location of an object's weight. An object tips over when its cg is no longer directly above its base of support. |
Created by:
smurtab