OCR A Physics OCR Paper 1 2019

  • SECTION A

  • You should spend a maximum of [math]30\ \text{minutes}[/math] on this section.

  • Write your answer to each question in the box provided.

  • Answer all the questions

  • 1. Which set of prefixes A, B, C or D are in order of increasing magnitude?
  • A. micro, milli, centi, kilo
  • B. milli, centi, micro, kilo
  • C. kilo, centi, milli, micro
    D. centi, micro, milli, kilo
  • Answer: A
  • Reason:
  • SI prefixes values are:
  • [math]\text{micro}\ (\mu)=10^{-6}=0.000001[/math]
  • [math]\text{milli}\ (m)=10^{-3}=0.001[/math]
  • [math]\text{centi}\ (c)=10^{-2}=0.01[/math]
  • [math]\text{kilo}\ (k)=10^{3}=1000[/math]
  • Increasing magnitude means smallest → largest:
  • [math]\text{micro}<\text{milli}<\text{centi}<\text{kilo}[/math]
  • So correct order is:
  • [math]10^{-6}<10^{-3}<10^{-2}<10^{3}[/math]
  • Therefore, Option A is correct.
  • 2. A paper cone is held above the ground and dropped. It falls vertically and reaches terminal velocity before it hits the ground.
  • Which statement correctly describes the resultant force on the falling cone before it reaches terminal velocity?
  • A. decreasing and upwards
  • B. decreasing and downwards
  • C. increasing and downwards
  • D. increasing and upwards
  • Answer: B
  • Reason:
  • Forces on cone:
  • – Weight acts downward (constant).
  • – Air resistance acts upward.
  • As speed increases:
  • – Air resistance increases.
  • – Resultant force decreases.
  • Before terminal velocity:
  • [math]\text{Weight}>\text{Air Resistance}[/math]
  • So resultant force is:
  • – downward
  • – decreasing
  • 3. A solid cylindrical glass rod has length [math]20.0\pm0.1\ \text{cm}[/math] and diameter [math]5.00\pm0.01\ \text{mm}[/math].
  • What is the percentage uncertainty in the calculated volume of this rod?
  • A. [math]0.1\text{%}[/math]
  • B. [math]0.2\text{%}[/math]
  • C. [math]0.7\text{%}[/math]
  • D. [math]0.9\text{%}[/math]
  • Answer: D
  • Reason:
  • Length [math]=l=20.0\pm0.1\ \text{cm}[/math]
  • Diameter [math]=d=5.00\pm0.01\ \text{mm}[/math]
  • Volume of cylinder:
  • [math]V=\pi r^{2}l[/math]
  • Percentage uncertainty in length:
  • [math]\frac{0.1}{20.0}\times100[/math]
  • [math]=0.5\text{%}[/math]
  • Percentage uncertainty in diameter:
  • [math]\frac{0.01}{5.00}\times100[/math]
  • [math]=0.2\text{%}[/math]
  • Since diameter is squared:
  • [math]2(0.2\text{%})=0.4\text{%}[/math]
  • Add uncertainties:
  • [math]0.5\text{%}+0.4\text{%}=0.9\text{%}[/math]
  • 4. A simple harmonic oscillator has maximum speed [math]24\ \text{m}\ \text{s}^{-1}[/math] and amplitude [math]5.6\ \text{cm}[/math].
  • What is its angular frequency?
  • A. [math]0.23\ \text{rad}\ \text{s}^{-1}[/math]
  • B. [math]21\ \text{rad}\ \text{s}^{-1}[/math]
  • C. [math]68\ \text{rad}\ \text{s}^{-1}[/math]
  • D. [math]430\ \text{rad}\ \text{s}^{-1}[/math]
  • Answer: D
  • Reason:
  • A simple harmonic oscillator has:
  • Maximum speed [math]= 24\ \text{m}\ \text{s}^{-1}[/math]
  • Amplitude [math]= 5.6\ \text{cm} = 0.056\ \text{m}[/math]
  • Find angular frequency.
  • For SHM:
  • [math]v_{\text{max}} = \omega A[/math]
  • So:
  • [math]\omega = \frac{v_{\text{max}}}{A}[/math]
  • Substitute values:
  • [math]\omega = \frac{24}{0.056}[/math]
  • [math]\omega = 428.57 \approx 430\ \text{rad}\ \text{s}^{-1}[/math]
  • 5. A car is dripping oil at a steady rate on a straight road. The road is divided into four sections A, B, C, and D.
  • Which section of the road shows the car travelling at a constant speed?
  • Answer: C
  • Reason:
  • Since oil drops fall at equal time intervals, the distance between drops shows how far the car travels in equal times.
  • – Large spacing = high speed
  • – Small spacing = low speed
  • – Equal spacing = constant speed
  • In section C, the oil drops are equally spaced.
  • This means:
  • – In every equal time interval, the car covers the same distance.
  • – So, speed is constant.
  • Hence, constant speed = Section C.
  • 6. The Earth is surrounded by a gravitational field.
  • Which of the following statements is/are correct about the gravitational field lines near the surface of the Earth.
  • 1. They are parallel.
  • 2. They show the direction of the force on a small mass.
  • 3. They are equally spaced.
  • A. Only 1
  • B. Only 1 and 2
  • C. Only 2 and 3
  • D. 1, 2 and 3
  • Answer: D
  • Reason:
  • “They are parallel.”
  • True
  • Near Earth’s surface field lines are nearly parallel.
  • “They show direction of force on a small mass.”
  • True
  • Field lines indicate force direction.
  • “They are equally spaced.”
  • True
  • Uniform field → equal spacing.
  • D (1, 2 and 3)
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