Understanding Motion: Vectors, Scalars, and Acceleration

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Questions and Answers

Consider a scenario where a projectile is launched at an angle $\theta$ with respect to the horizontal, experiencing air resistance proportional to the square of its velocity. Which of the following statements regarding its trajectory is most accurate?

  • The trajectory remains perfectly parabolic, but the range is reduced compared to the ideal case without air resistance.
  • The horizontal range is shorter, and the maximum height is lower than in the absence of air resistance; the trajectory is asymmetric, with a steeper descent. (correct)
  • The horizontal component of velocity decreases linearly, while the vertical component exhibits symmetric parabolic motion.
  • The projectile's time of flight is increased, and its maximum height is greater due to the drag force acting against gravity.

A relativistic particle with rest mass $m_0$ is moving at a velocity $v = 0.8c$, where $c$ is the speed of light. What is the percentage increase in its observed mass compared to its rest mass?

  • Approximately 33.3%
  • Approximately 80.0%
  • Approximately 166.7%
  • Approximately 66.7% (correct)

A car accelerates uniformly from rest on a level surface. Neglecting air resistance and considering only the effects of static friction between the tires and the road, under what conditions will the maximum possible acceleration be achieved?

  • The maximum acceleration is independent of both the coefficient of static friction and the mass of the car.
  • When the coefficient of static friction is maximized, and the mass of the car is minimized. (correct)
  • When the coefficient of static friction is minimized, and the mass of the car is maximized.
  • When the product of the coefficient of static friction and the mass of the car is maximized.

Consider two identical springs connected in series. If a mass $m$ is attached to the combination, the system oscillates with a frequency $f$. What would be the oscillation frequency if the same two springs were connected in parallel with the same mass $m$?

<p>$2f$ (C)</p> Signup and view all the answers

Two cars, A and B, are moving towards each other on a straight road. Car A has a velocity of $v_A$ and car B has a velocity of $v_B$. At time $t=0$, they are separated by a distance $d$. Both cars begin braking simultaneously, each with a constant deceleration of magnitude $a$. What is the minimum value of $d$ required to prevent a collision?

<p>$\frac{v_A^2 + v_B^2}{2a}$ (A)</p> Signup and view all the answers

A block of mass $m$ slides down an inclined plane tilted at an angle $\theta$ with respect to the horizontal. The coefficient of kinetic friction between the block and the plane is $\mu_k$. What is the condition for the block to accelerate down the plane?

<p>$\tan(\theta) &gt; \mu_k$ (D)</p> Signup and view all the answers

An object is launched vertically upwards with an initial velocity $v_0$ in a non-uniform gravitational field where $g(y) = g_0(1 + ky)$, with $y$ being the vertical distance from the launch point and $k$ a positive constant. What is the maximum height reached by the object?

<p>$\frac{v_0^2}{2g_0}(1 - \frac{kv_0^2}{3g_0})$ (C)</p> Signup and view all the answers

A car is designed with crumple zones that allow for a maximum deceleration of $a_{max}$ during a collision. If the car, moving at an initial velocity $v_0$, undergoes a head-on collision, what is the minimum crumple distance $d$ required to ensure the deceleration does not exceed $a_{max}$?

<p>$d = \frac{v_0^2}{2a_{max}}$ (B)</p> Signup and view all the answers

Consider a classical system consisting of a particle of mass $m$ moving in a potential $V(x) = kx^4$, where $k$ is a positive constant. What is the approximate relationship between the average kinetic energy $T$ and the average potential energy $V$ for this system?

<p>$T = 3V$ (C)</p> Signup and view all the answers

A car is equipped with an advanced anti-lock braking system (ABS) that modulates the braking force to maintain the wheels at the verge of slipping (i.e., maximizing static friction). How does this system primarily enhance car safety compared to a car without ABS during emergency braking scenarios?

<p>By allowing the driver to maintain steering control while braking heavily, preventing skidding. (C)</p> Signup and view all the answers

A particle moves in a viscous medium, experiencing a drag force proportional to the square of its velocity ($F_d = -bv^2$). If the particle is released from rest under the influence of gravity ($F_g = mg$), determine the terminal velocity ($v_t$) of the particle.

<p>$v_t = \sqrt{\frac{mg}{b}}$ (D)</p> Signup and view all the answers

A drag racer accelerates from rest with a constant acceleration $a$ over a quarter-mile (402.3 meters). Assuming negligible air resistance, what minimum average power must the engine deliver to achieve this, given the racer has a mass $m$?

<p>$P = \frac{1}{2}ma\sqrt{2a \cdot 402.3}$ (A)</p> Signup and view all the answers

A car's suspension system is modeled as a damped harmonic oscillator with mass $m$, spring constant $k$, and damping coefficient $b$. Determine the condition for the system to be critically damped, ensuring the quickest return to equilibrium without oscillation after a disturbance.

<p>$b = 2\sqrt{km}$ (D)</p> Signup and view all the answers

Imagine a modified Newton's cradle with four balls. Initially, balls 1 and 2 are swung together from the left, impacting balls 3 and 4 at rest. Assuming perfectly elastic collisions, what is the resulting motion of the balls after the impact?

<p>Balls 1 and 2 stop, and balls 3 and 4 swing out together with the same velocity as balls 1 and 2 initially. (B)</p> Signup and view all the answers

A train is traveling at a constant velocity $v$ relative to the ground. A passenger walks from the back to the front of the train with a constant velocity $u$ relative to the train. Simultaneously, the train passes through a tunnel of length $L$. What is the time interval during which the passenger is inside the tunnel?

<p>$L/v$ (B)</p> Signup and view all the answers

Consider a car moving on a circular track with radius $r$. The car starts from rest and its speed increases at a constant rate $a_t$ (tangential acceleration). Determine the angle $\theta$ (relative to the starting point) at which the magnitudes of the tangential and centripetal accelerations are equal.

<p>$\theta = 2 , \text{radians}$ (C)</p> Signup and view all the answers

A block of mass $m$ is attached to a spring with spring constant $k$ and oscillates on a horizontal frictionless surface. If the block is also subject to a velocity-dependent damping force $F = -bv$, what is the angular frequency ($\omega$) of the damped oscillations?

<p>$\omega = \sqrt{\frac{k}{m} - \frac{b^2}{4m^2}}$ (D)</p> Signup and view all the answers

A car accelerates uniformly from rest to a speed $v$ in time $t$. What fraction of the total distance traveled during this acceleration is covered in the first half of the time interval ($t/2$)?

<p>$1/4$ (B)</p> Signup and view all the answers

Two objects, A and B, of masses $m$ and $2m$ respectively, are connected by a massless string that passes over a frictionless pulley. Initially, object A is held at rest on a table, and object B hangs freely. If the system is released, what is the acceleration of object A across the table, assuming the table is frictionless?

<p>$2g/3$ (B)</p> Signup and view all the answers

A rocket in deep space (no external forces) expels exhaust gases at a constant velocity $v_e$ relative to the rocket. If the rocket's initial mass is $m_0$ and its final mass is $m_f$, what is the rocket's final velocity $v$ if it started from rest?

<p>$v = v_e \ln(\frac{m_0}{m_f})$ (A)</p> Signup and view all the answers

A car accelerates from rest with a constant tangential acceleration on a flat, horizontal, circular track. Which of the following statements accurately describes how the required coefficient of static friction between the tires and the road changes as the car's speed increases?

<p>The required coefficient of static friction increases with the square of the car's speed. (D)</p> Signup and view all the answers

In a ballistic pendulum experiment, a bullet of mass $m$ is fired into a stationary block of mass $M$ suspended by a massless string. The bullet embeds itself in the block, and the block swings to a maximum height $h$. What is the initial speed of the bullet ($v$) before the collision?

<p>$v = \frac{m+M}{m} \sqrt{2gh}$ (C)</p> Signup and view all the answers

A disc rolls without slipping down an inclined plane. What fraction of its total kinetic energy is rotational kinetic energy?

<p>$1/3$ (C)</p> Signup and view all the answers

A car merges onto a highway, increasing its speed from $v_1$ to $v_2$ over a distance $d$ with non-constant acceleration. Assuming the acceleration varies linearly with distance, $a(x) = Ax + B$, determine the constants $A$ and $B$ in terms of $v_1$, $v_2$, and $d$.

<p>$A = \frac{v_2^2 - v_1^2}{2d^2}$, $B = \frac{v_1^2}{2d}$ (D)</p> Signup and view all the answers

A small block is placed on a rotating turntable at a distance $r$ from the center. The turntable's angular speed is slowly increased. If the coefficient of static friction between the block and the turntable is $\mu_s$, at what angular speed $\omega$ will the block begin to slip?

<p>$\omega = \sqrt{\frac{\mu_s g}{r}}$ (C)</p> Signup and view all the answers

A uniform rod of length $L$ and mass $M$ is pivoted at one end. What is the period of small oscillations for this physical pendulum?

<p>$T = 2\pi \sqrt{\frac{2L}{3g}}$ (B)</p> Signup and view all the answers

A projectile is launched with initial velocity $v_0$ at an angle $\theta$ above the horizontal from a height $h$ above the ground. If we consider air resistance to be negligible, what is the horizontal range $R$ of the projectile?

<p>$R = \frac{v_0 \cos(\theta)}{g} (v_0 \sin(\theta) + \sqrt{v_0^2 \sin^2(\theta) + 2gh})$ (A)</p> Signup and view all the answers

Consider a cyclist riding on a flat road. The cyclist exerts a constant force on the pedals. Which of the following is true regarding the cyclist's motion considering air resistance, which is proportional to the square of the velocity?

<p>The cyclist will reach a terminal velocity where the force exerted is equal to the drag force plus rolling resistance. (D)</p> Signup and view all the answers

A car is traveling at a constant speed $v$ around a banked curve with a radius $r$. The banking angle is $\theta$. Assuming no friction, what is the correct expression for the speed $v$ that allows the car to navigate the curve without any reliance on friction?

<p>$v = \sqrt{gr \tan(\theta)}$ (D)</p> Signup and view all the answers

A force $F(x) = -kx + bx^3$ acts on a particle, where $k$ and $b$ are positive constants. What is the nature of the equilibrium points for this system?

<p>There is an unstable equilibrium point at $x = 0$ and stable equilibrium points at $x = \pm \sqrt{\frac{k}{b}}$. (A)</p> Signup and view all the answers

Two cars of equal mass approach an intersection. Car A is traveling east at 20 m/s and car B is traveling north at 30 m/s. The cars collide inelastically and stick together. What is the approximate speed and direction (relative to north) of the wreckage immediately after the collision?

<p>Speed: 25 m/s, Direction: 33.7° east of north (D)</p> Signup and view all the answers

A point mass $m$ is constrained to move without friction on the inside of a vertical, circular hoop of radius $r$. If the mass is given an initial velocity at the bottom of the hoop, what minimum speed is required for the mass to make a complete revolution without losing contact with the hoop?

<p>$v = \sqrt{5gr}$ (C)</p> Signup and view all the answers

Flashcards

Scalar Quantity

A quantity with only magnitude (size), like speed or distance.

Vector Quantity

A quantity with both magnitude and direction, like velocity.

Distance

Total path length traveled.

Displacement

Straight-line distance from start to finish.

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Speed

How fast something is moving.

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Velocity

Speed with a direction.

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Acceleration

Rate of change of velocity. change in velocity / time.

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Newton's First Law

Object at rest stays at rest, object in motion stays in motion.

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Newton's Second Law

Force equals mass times acceleration. F = ma

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Newton's Third Law

For every action, equal and opposite reaction.

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km/h to m/s conversion

Divide km/h by 3.6.

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m/s to km/h conversion

Multiply m/s by 3.6

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Seatbelts

Prevent forward motion during sudden stops.

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Airbags

Increase the time to stop, reducing force.

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Crumple Zones

Absorb impact to lessen force on passengers.

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Distance-Time Graph

Steeper slope = faster speed. Flat line = stationary.

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Speed-Time Graph

Area under the graph = total distance. Upward slope = acceleration.

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Displacement-Time Graph

Shows distance compared to starting point. curved upwards = acceleration.

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Ticker Tape Analysis

Dots evenly spaced = constant speed. Spread out = accelerating.

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Study Notes

  • Motion is a common experience, seen in actions like walking, driving, or dropping a phone.

Vectors and Scalars

  • Scalar quantities describe the size of something (e.g., speed, distance).
  • Vector quantities have both size and direction.
  • A car going 60 km/h (scalar) vs. a car going 60 km/h east (vector).

Distance and Displacement

  • Distance is the total length traveled.
  • Displacement measures the straight-line distance from start to finish.
  • Walking 5 km around a block and returning home results in a 5 km distance and zero displacement.

Speed and Velocity

  • Speed is how fast something is moving (Speed = Distance ÷ Time).
  • Velocity is speed with a direction.
  • A car going 50 km/h north has a different velocity than a car going 50 km/h south, despite having the same speed.

Acceleration

  • Acceleration is the rate at which velocity changes.
  • Acceleration = (Final velocity - Initial velocity) ÷ Time, measured in m/s².
  • Accelerating from 0 to 10 m/s in 5 seconds equals 2 m/s² acceleration.
  • Deceleration means negative acceleration, occurring when an object slows down.
  • A car braking while moving forward has acceleration opposite to its velocity.

Newton’s Laws of Motion

  • First Law (Law of Inertia): Objects at rest stay at rest, and objects in motion stay in motion unless acted upon by an external force.
  • A person lurches forward on a bus when it stops suddenly.
  • Second Law: Force = Mass × Acceleration (F = ma).
  • It's harder to push a heavy shopping cart as it requires more force for the same acceleration.
  • High-performance sports cars have high acceleration due to strong engines (high force) and low mass.
  • Third Law: For every action, there is an equal and opposite reaction.
  • Jumping off a boat makes the boat move backward.

Unit Conversions

  • To convert km/h to m/s, divide by 3.6.
  • To convert m/s to km/h, multiply by 3.6.
  • 72 km/h is equal to 20 m/s (72 ÷ 3.6 = 20).

Car Safety

  • Car safety features like seatbelts, airbags, and crumple zones are based on Newton’s Laws.
  • Seatbelts prevent forward motion when a car stops suddenly (Newton’s First Law).
  • Airbags increase the time to stop, reducing acceleration and force (Newton’s Second Law).
  • Crumple zones absorb impact to reduce the force felt by passengers.
  • Modern cars are designed to crumple in specific areas to enhance safety.

Graphing Motion

  • Distance-time graphs: Steeper slope indicates faster speed; a flat line means stationary.
  • Speed-time graphs: Area under the graph shows total distance; upward slope means acceleration; downward slope means deceleration.
  • Displacement-time graphs: Curves upwards when acceleration is happening, showing distance from starting point

Ticker Tape Analysis

  • A ticker timer marks dots on tape at regular intervals (e.g., every 0.02 seconds).
  • Evenly spaced dots indicate constant speed.
  • Dots spreading out show acceleration.
  • Dots getting closer indicate deceleration.
  • Used to calculate acceleration and velocity in lab experiments.

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