Practice Test 12 - High School Physics

20 questions. Answer them in any order, then submit to see your score and every explanation.

A sensor measures temperature, which is a natural analog quantity that varies continuously. The sensor output is sent to a microcontroller that uses digital logic (binary 0 and 1). What must happen for the microcontroller to store and process the temperature reading digitally?
A $10\,\text{kg}$ box is pulled across a horizontal floor by an applied force $F_{\text{app}}=60\,\text{N}$ at $30^\circ$ above the horizontal (to the right). Assume $g=10\,\text{m/s}^2$ . Which expression best gives the normal force magnitude $F_N$ on the box (assuming the box does not accelerate vertically)?
A $m=1500\,\text{kg}$ SUV crashes at $v=25\,\text{m/s}$ . You must choose a front-end crumple distance $d$ to minimize average force while meeting the safety limit $F_{\max}=3.0\times10^5\,\text{N}$ . Vehicle design constraint: $d\le 0.80\,\text{m}$ . Which statement is correct? (Use $d_{\min}=\frac{\tfrac12 mv^2}{F_{\max}}$ .)
A small camping power system uses a battery that converts chemical → electrical. A $5.0\,\text{V}$ USB load draws $I=2.0\,\text{A}$ for $3.0\,\text{h}$ . The battery pack is rated at $10\,\text{Ah}$ at $5.0\,\text{V}$ , but only $80\%$ of its stored energy is usable due to internal losses and cutoff voltage limits. Does the battery meet the requirement? (Compare usable energy to required energy.)
An electron beam is fired at a thin crystal. The electrons produce a pattern of bright rings/spots on a detector screen, similar to X-ray diffraction patterns. Which model best explains the formation of this pattern?
A $2.5\,\text{kg}$ object is pulled along a horizontal surface. A constant $40\,\text{N}$ force acts in the direction of motion while a constant $10\,\text{N}$ friction force acts opposite the motion. Over a displacement of $4.0\,\text{m}$ , what is the net work done on the object?
Two objects are separated by the same distance $r$ . Object 1 has mass $m_1 = 1.0\,\text{kg}$ and charge $q_1 = +2.0\times 10^{-6}\,\text{C}$ ; object 2 has mass $m_2 = 3.0\,\text{kg}$ and charge $q_2 = -2.0\times 10^{-6}\,\text{C}$ . Using $F_{\text{grav}} = Gm_1m_2/r^2$ and $F_{\text{elec}} = kq_1q_2/r^2$ , which expression correctly gives the ratio $F_{\text{elec}}/F_{\text{grav}}$ (including sign to indicate attraction vs repulsion)?
A data logger can transmit readings as an analog voltage level or as a digital packet with a checksum (error detection). The channel sometimes flips bits due to interference. Which statement best describes a practical advantage of the digital method in this situation?
A straight vertical wire passes through a hole in a table. Conventional current $I=2.0\,\text{A}$ flows upward (out of the table surface). A small compass is placed on the table 5 cm east (to the right) of the wire to investigate the magnetic field produced by the current. When the current is switched on, in which direction does the compass needle's north end point due to the wire's magnetic field at the compass location?
In a lab demo, a 200-turn coil is connected to a galvanometer to form a closed circuit. A bar magnet is moved straight into the center of the coil and then held still inside it. When will the galvanometer show a nonzero deflection (induced current)?
A seat belt pretensioner tightens the belt early in a crash so the occupant begins decelerating sooner with the car, rather than moving forward and then stopping abruptly against the belt. Which physics-based argument best explains how pretensioning can reduce injury risk?
Two hockey pucks slide on nearly frictionless ice and collide in 1D. Puck A has mass $m_A=0.20\ \text{kg}$ and initial velocity $v_{A i}=+10\ \text{m/s}$ (right). Puck B has mass $m_B=0.10\ \text{kg}$ and is initially at rest ( $v_{B i}=0$ ). After an elastic collision, Puck A is observed to move at $v_{A f}=+3.3\ \text{m/s}$ (right). Taking rightward as positive, what is Puck B's final velocity $v_{B f}$ (from momentum conservation)?
A metal spoon (stainless steel) starts at 20°C and is placed into a mug of hot tea at 80°C. After 1 minute, the spoon handle above the tea feels warmer even though it is not touching the tea. Which thermal energy transfer mechanism is primarily responsible for thermal energy moving along the spoon from the submerged end toward the handle?
A $10\,\text{kg}$ crate slides down a frictionless ramp from a vertical height of $6.0\,\text{m}$ , then crosses a rough horizontal floor where the friction force is $40\,\text{N}$ . The crate comes to rest on the rough floor. Using $g=10\,\text{m/s}^2$ , how far does it slide on the rough floor before stopping? Energy tracking: initial $PE_g$ $\rightarrow$ $KE$ at bottom $\rightarrow$ thermal energy from friction until $KE=0$ .
A town is comparing two ways to deliver live TV from a broadcast tower to homes 30 km away. Option 1 is analog TV, where interference shows up directly in the picture. Option 2 is digital TV, which uses error correction and works as long as the receiver can still distinguish bits. During a thunderstorm, interference increases and the effective SNR drops from about 35 dB to 15 dB. What difference would viewers most likely observe as the storm worsens?
A 1200 kg car traveling at 20 m/s hits a rigid barrier. Engineers can vary the crumple-zone deformation distance $d$ . To meet a safety requirement, the average impact force on the car must satisfy $F\le 4.0\times 10^5\ \text{N}$ . Packaging constraints limit the crumple zone to at most $d_{\max}=0.80\ \text{m}$ . What is the minimum crumple distance required, and does it fit within the constraint? (Use $F=\text{KE}/d$ with $\text{KE}=\tfrac12 mv^2$ .)
A $20\,\text{kg}$ box rests on a frictionless $30^\circ$ incline (angle measured from the horizontal). Forces on the box: weight $F_g$ (↓), normal force $F_N$ (perpendicular to the incline), and no friction. Using $g=10\,\text{m/s}^2$ , what is the magnitude of the normal force $F_N$ ?
Visible light in a vacuum travels at $c = 3.0\times10^8\ \text{m/s}$ . A green laser has wavelength $\lambda = 532\ \text{nm}$ ( $532\times10^{-9}\ \text{m}$ ). What is its frequency $f$ ? (Use $f=c/\lambda$ .)
A head-on collision occurs on a low-friction track. Cart A has mass $1.0\,\text{kg}$ and initial velocity $v_{A i} = +5.0\,\text{m/s}$ (right). Cart B has mass $1.0\,\text{kg}$ and initial velocity $v_{B i} = -3.0\,\text{m/s}$ (left). The collision is perfectly elastic. What are the final velocities $(v_{A f}, v_{B f})$ immediately after the collision?
In designing an investigation comparing elastic vs perfectly inelastic collisions, students use two dynamics carts on a level low-friction track. They can attach magnetic bumpers (elastic) or Velcro bumpers (perfectly inelastic). Motion sensors measure velocities immediately before and after the collision, and a balance measures masses. Which procedure best tests momentum conservation for both collision types?

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