TRUE OR FALSE — MOTION AND PRESSURE
Types of Motion
1. Motion
Statement 1: Motion is the change in position of an object over time relative to a reference point.
ANSWER: True
Statement 2: Motion is described by parameters such as displacement, distance, velocity, acceleration and time.
ANSWER: True
Statement 3: Motion can be described without any reference to a reference point.
ANSWER: False — Motion is always described relative to a reference point.
2. Rectilinear Motion
Statement 1: Rectilinear motion occurs along a straight line.
ANSWER: True
Statement 2: A car driving on a straight highway is an example of rectilinear motion.
ANSWER: True
Statement 3: Rectilinear motion occurs along the path of a circle.
ANSWER: False — That describes circular motion, not rectilinear motion.
3. Circular Motion
Statement 1: Circular motion occurs along the path of a circle.
ANSWER: True
Statement 2: A ball tied to a string and swung around in a circular path demonstrates circular motion.
ANSWER: True
Statement 3: Circular motion is motion along a straight line.
ANSWER: False — That describes rectilinear motion, not circular motion.
4. Oscillatory Motion
Statement 1: Oscillatory motion repeats back and forth.
ANSWER: True
Statement 2: A swinging pendulum demonstrates oscillatory motion.
ANSWER: True
Statement 3: Oscillatory motion has no predictable pattern.
ANSWER: False — Oscillatory motion follows a repeating, predictable pattern.
5. Rotational Motion (Spin Motion)
Statement 1: Rotational motion is also called spin motion.
ANSWER: True
Statement 2: A spinning coin or bottle cap demonstrates rotational motion.
ANSWER: True
Statement 3: Rotational motion describes back-and-forth repeating movement.
ANSWER: False — That describes oscillatory motion, not rotational motion.
6. Random (Brownian) Motion
Statement 1: Random motion has no predictable pattern.
ANSWER: True
Statement 2: Random motion is also associated with a scientist studying the behaviour of small particles suspended in a fluid.
ANSWER: True
Statement 3: Random motion follows a fixed, repeating pattern.
ANSWER: False — Random (Brownian) motion is unpredictable, not repeating.
Newton's Laws and Related Concepts
7. Equations of Motion
An object starts with an initial velocity of $2.0\text{ m/s}$ and accelerates at $3.0\text{ m/s}^2$ for $2.0\text{ s}$.
Statement 1: Given the data above, the final velocity works out to 8.0 m/s.
ANSWER: True — $v = u+at = 2.0+(3.0\times2.0) = 8.0\text{ m/s}$.
Statement 2: If the time were instead $4.0\text{ s}$, the final velocity would be 14 m/s.
ANSWER: True — $v = 2.0+(3.0\times4.0) = 14\text{ m/s}$.
Statement 3: If the acceleration were instead $4.0\text{ m/s}^2$ over the original $2.0\text{ s}$, the final velocity would be 8.0 m/s still.
ANSWER: False — $v = 2.0+(4.0\times2.0) = 10\text{ m/s}$, not 8.0 m/s.
8. Motion Under Gravity
An object is dropped from rest and falls freely under gravity for $2.0\text{ s}$. [Take $g = 10\text{ m/s}^2$.]
Statement 1: Given the data above, the velocity after falling works out to 20 m/s.
ANSWER: True — $v = gt = 10\times2.0 = 20\text{ m/s}$.
Statement 2: If the object fell for $3.0\text{ s}$ instead, its velocity would be 30 m/s.
ANSWER: True — $v = 10\times3.0 = 30\text{ m/s}$.
Statement 3: If the object fell for $1.0\text{ s}$ instead, its velocity would be 20 m/s still.
ANSWER: False — $v = 10\times1.0 = 10\text{ m/s}$, not 20 m/s.
9. Newton's First Law (Law of Inertia)
Statement 1: Newton's First Law states that a body continues in its state of rest or uniform motion in a straight line unless acted upon by an unbalanced force.
ANSWER: True
Statement 2: Newton's First Law is also called the Law of Inertia.
ANSWER: True
Statement 3: Newton's First Law states that force equals mass times acceleration.
ANSWER: False — That describes Newton's Second Law, not the First Law.
10. Inertia
Statement 1: Inertia describes the tendency of an object to resist a change in its state of motion.
ANSWER: True
Statement 2: A pile of books staying in place when a tablecloth is yanked out from under them demonstrates inertia.
ANSWER: True
Statement 3: Inertia is a law, not a property of matter.
ANSWER: False — Inertia is a property of matter, described by Newton's First Law.
11. Newton's Second Law (Law of Acceleration)
A resultant force of $10\text{ N}$ acts on an object of mass $2.0\text{ kg}$.
Statement 1: Given the data above, the acceleration works out to 5.0 m/s².
ANSWER: True — $a = F/m = 10/2.0 = 5.0\text{ m/s}^2$.
Statement 2: If the mass were instead $5.0\text{ kg}$, the acceleration would be 2.0 m/s².
ANSWER: True — $a = 10/5.0 = 2.0\text{ m/s}^2$.
Statement 3: If the force were instead $20\text{ N}$ on the original $2.0\text{ kg}$ mass, the acceleration would be 5.0 m/s² still.
ANSWER: False — $a = 20/2.0 = 10\text{ m/s}^2$, not 5.0 m/s².
12. Newton's Third Law (Law of Action and Reaction)
Statement 1: Newton's Third Law states that for every action, there is an equal and opposite reaction.
ANSWER: True
Statement 2: A balloon flying across a room as air escapes from it demonstrates Newton's Third Law.
ANSWER: True
Statement 3: Newton's Third Law states that a body at rest stays at rest unless acted upon by an unbalanced force.
ANSWER: False — That describes Newton's First Law, not the Third Law.
13. Unbalanced Force
Statement 1: An unbalanced force occurs when the forces acting on an object do not cancel each other out.
ANSWER: True
Statement 2: An unbalanced force results in a net force that causes an object to accelerate.
ANSWER: True
Statement 3: An unbalanced force always results in zero net force.
ANSWER: False — An unbalanced force produces a nonzero net force, causing acceleration.
14. Momentum
An object of mass $3.0\text{ kg}$ moves with a velocity of $4.0\text{ m/s}$.
Statement 1: Given the data above, the momentum works out to 12 kg·m/s.
ANSWER: True — $p = mv = 3.0\times4.0 = 12\text{ kg}\cdot\text{m/s}$.
Statement 2: If the velocity were instead $8.0\text{ m/s}$, the momentum would be 24 kg·m/s.
ANSWER: True — $p = 3.0\times8.0 = 24\text{ kg}\cdot\text{m/s}$.
Statement 3: If the mass were instead $6.0\text{ kg}$ at the original $4.0\text{ m/s}$, the momentum would be 12 kg·m/s still.
ANSWER: False — $p = 6.0\times4.0 = 24\text{ kg}\cdot\text{m/s}$, not 12 kg·m/s.
Graphs of Motion
15. Distance-Time Graph
On a distance-time graph, an object covers $20\text{ m}$ in $4.0\text{ s}$.
Statement 1: Given the data above, the slope (speed) works out to 5.0 m/s.
ANSWER: True — slope $= 20/4.0 = 5.0\text{ m/s}$.
Statement 2: If the object covered $40\text{ m}$ in the same $4.0\text{ s}$, the slope would be 10 m/s.
ANSWER: True — slope $= 40/4.0 = 10\text{ m/s}$.
Statement 3: If the object covered $20\text{ m}$ in $2.0\text{ s}$ instead, the slope would be 5.0 m/s still.
ANSWER: False — slope $= 20/2.0 = 10\text{ m/s}$, not 5.0 m/s.
16. Position-Time Graph (Displacement-Time Graph)
Statement 1: A position-time graph is closely related to a distance-time graph.
ANSWER: True
Statement 2: Values on a position-time graph can be positive or negative depending on the chosen reference point.
ANSWER: True
Statement 3: A position-time graph can never show negative values.
ANSWER: False — Position-time graph values can be negative, depending on the reference point chosen.
17. Velocity-Time Graph
On a velocity-time graph, an object accelerates uniformly from rest to $8.0\text{ m/s}$ over $4.0\text{ s}$.
Statement 1: Given the data above, the displacement (area under the graph) works out to 16 m.
ANSWER: True — area $= \tfrac{1}{2}\times4.0\times8.0 = 16\text{ m}$.
Statement 2: If the object instead reached $12\text{ m/s}$ over the same $4.0\text{ s}$, the displacement would be 24 m.
ANSWER: True — area $= \tfrac{1}{2}\times4.0\times12 = 24\text{ m}$.
Statement 3: If the object reached $8.0\text{ m/s}$ over $8.0\text{ s}$ instead, the displacement would be 16 m still.
ANSWER: False — area $= \tfrac{1}{2}\times8.0\times8.0 = 32\text{ m}$, not 16 m.
Pressure
18. Pressure
A force of $20\text{ N}$ acts on an area of $4.0\text{ m}^2$.
Statement 1: Given the data above, the pressure works out to 5.0 Pa.
ANSWER: True — $P = F/A = 20/4.0 = 5.0\text{ Pa}$.
Statement 2: If the area were instead $2.0\text{ m}^2$, the pressure would be 10 Pa.
ANSWER: True — $P = 20/2.0 = 10\text{ Pa}$.
Statement 3: If the force were instead $40\text{ N}$ on the original $4.0\text{ m}^2$ area, the pressure would be 5.0 Pa still.
ANSWER: False — $P = 40/4.0 = 10\text{ Pa}$, not 5.0 Pa.
19. Hydrostatic Pressure
A fluid has a density of $1.0\times10^3\text{ kg/m}^3$ (density of water, to 2 s.f.) and a depth of $2.0\text{ m}$. [Take $g = 10\text{ m/s}^2$.]
Statement 1: Given the data above, the hydrostatic pressure works out to $2.0\times10^4$ Pa.
ANSWER: True — $P = h\rho g = 2.0\times(1.0\times10^3)\times10 = 2.0\times10^4\text{ Pa}$.
Statement 2: If the depth were instead $4.0\text{ m}$, the hydrostatic pressure would be $4.0\times10^4$ Pa.
ANSWER: True — $P = 4.0\times(1.0\times10^3)\times10 = 4.0\times10^4\text{ Pa}$.
Statement 3: If the depth were instead $1.0\text{ m}$, the hydrostatic pressure would be $2.0\times10^4$ Pa still.
ANSWER: False — $P = 1.0\times(1.0\times10^3)\times10 = 1.0\times10^4\text{ Pa}$, not $2.0\times10^4$ Pa.
20. Pascal's Principle
Statement 1: Pascal's Principle states that a pressure change at any point in a confined fluid is transmitted equally throughout the fluid.
ANSWER: True
Statement 2: Hydraulic systems and brake systems rely on Pascal's Principle.
ANSWER: True
Statement 3: Pascal's Principle states that pressure changes are only transmitted in the direction they are applied.
ANSWER: False — A pressure change is transmitted equally throughout the confined fluid, not only in one direction.
21. Hydraulic Press
A hydraulic press has a small piston of area $2.0\text{ m}^2$ and a large piston of area $8.0\text{ m}^2$. An effort force of $10\text{ N}$ is applied to the small piston.
Statement 1: Given the data above, the output force on the large piston works out to 40 N.
ANSWER: True — $F_2 = F_1\times(A_2/A_1) = 10\times(8.0/2.0) = 40\text{ N}$.
Statement 2: If the effort force were instead $20\text{ N}$, the output force would be 80 N.
ANSWER: True — $F_2 = 20\times(8.0/2.0) = 80\text{ N}$.
Statement 3: If the large piston's area were instead $4.0\text{ m}^2$, with the original $10\text{ N}$ effort, the output force would be 40 N still.
ANSWER: False — $F_2 = 10\times(4.0/2.0) = 20\text{ N}$, not 40 N.
22. Hydraulic Brakes
Statement 1: A hydraulic braking system converts a driver's foot pressure into hydraulic pressure to apply friction on the wheels.
ANSWER: True
Statement 2: A hydraulic braking system relies on pressure being transmitted equally throughout a fluid.
ANSWER: True
Statement 3: A hydraulic braking system operates without relying on any fluid.
ANSWER: False — Hydraulic brakes rely on a fluid to transmit pressure throughout the system.