OAR Mechanical Comprehension Review Exam Questions and Answers An increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy - Correct Answers ✅Bernoulli's Principle The absolute pressure and volume of a gas are inversely proportional, as long as the temperature is held constant.
Example: if volume is cut in half, then the pressure is
doubled. - Correct Answers ✅Boyle's Law Gasses expand when heated. If the temperature on a gas is increased, the volume of the gas increases. Volume and temperature of a gas are directly proportional at a constant pressure. - Correct Answers ✅Charles' Law Objects in motion (rest) will stay in motion (rest) unless acted upon by an outside force
Examples of outside forces: friction, air resistance - Correct
Answers ✅Newton's First Law Force = Mass x Acceleration (F = MA) - Correct Answers ✅Newton's Second Law When any object exerts a force on another object, the other object exerts the opposite force back on the original object (same magnitude)
Example: the plane engine accelerates air out the back, the
opposite reaction to that force is thrust (makes a plane move 1 / 4
OAR Mechanical Comprehension Review Exam Questions and Answers forward). Cars also have thrust to move them forward (same idea)
Example: filling a balloon/letting it go (air comes out the back
and the balloon moves forward) - Correct Answers ✅Newton's Third Law Scalars are quantities that only have magnitude (or size), while vectors have both magnitude and direction - Correct Answers ✅Scalar vs Vector Quantities Speed is a scalar quantity and has no direction, unlike velocity - Correct Answers ✅Speed Any process where the velocity changes (how quickly something changes from one velocity to another). Since velocity is a speed and a direction, there are only two ways
for you to accelerate: change your speed or change your
direction—or change both. - Correct Answers ✅Acceleration Occurs when an object is in the air and experiencing only the force of gravity.The horizontal component of velocity does not change (throughout flight) 2 / 4
OAR Mechanical Comprehension Review Exam Questions and Answers The vertical acceleration due to gravity affects the vertical component of velocity (because gravity only acts downwards)
- Correct Answers ✅Projectile motion
Gravity of the Earth imposes an acceleration of g = 9.8 m/s2 or 32 ft/s2 - Correct Answers ✅Gravity
Conservation of linear momentum: expresses the fact that a
body in motion retains its total momentum, unless an external force is applied to it. In an isolated system (such as the universe), there are no external forces, so momentum is always conserved.
Example: If an ice-skater is spinning and tucks her arms in,
will the angular momentum increase or decrease? It is conserved. - Correct Answers ✅Linear Momentum Simple rotation is when an object rotates around a point at a constant speed. A point will have a greater linear speed when it is farther from the center of rotation.
Example: A potter is spinning the clay wheel at a constant
speed of one revolution/sec. The clay that is 6 inches from the center is going faster than the clay 3 inches from the center. The clay directly in the center of the wheel has no linear velocity. - Correct Answers ✅Rotational kinematics Force = Mass x Acceleration 3 / 4
OAR Mechanical Comprehension Review Exam Questions and Answers
Mass [KG]: quantity of matter in an object
Acceleration: how quickly an object changes from one
velocity to another (= ΔV/ΔT)
Force [Newtons]: net vector sum which causes acceleration of
an object (magnitude and direction) - Correct Answers ✅Force The perpendicular force exerted on an object that is resting on some other surface
Example: if a box is resting on a horizontal surface, the
normal force is directed upwards through the box (the opposite, downward force is the weight of the box) - Correct Answers ✅Normal Force Drag force occurs when an object moves through some fluid (either liquid or gas) and experiences a force that opposes the motion of the object.
Example: The engine of an airplane uses the force of thrust to
move it forward. The equal opposite reaction to thrust is DRAG (specifically pressure drag). Try to minimize this type of drag by making the airplane as aerodynamic as possible - Correct Answers ✅Drag force An object is in equilibrium when the sum of all forces acting on the object is zero. When the forces on an object sum to zero, the object does not accelerate. Equilibrium occurs when the forces in the y-direction sum to zero, forces in the x
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