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Figure 5 shows a simplified catapult used to hurl projectiles a long way - AQA - A-Level Physics - Question 4 - 2019 - Paper 1

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Figure 5 shows a simplified catapult used to hurl projectiles a long way. The counterweight is a wooden box full of stones attached to one end of the beam. The proj... show full transcript

Worked Solution & Example Answer:Figure 5 shows a simplified catapult used to hurl projectiles a long way - AQA - A-Level Physics - Question 4 - 2019 - Paper 1

Step 1

04.1-1 Suggest how the pivot position achieves this.

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Answer

The pivot is positioned at the center of mass of the beam and empty wooden box. This ensures that the moments about the pivot from the weight of the beam and the box balance each other out, resulting in no net torque and thus no effect on the tension in the rope.

Step 2

04.1-2 Calculate the tension in the rope.

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Answer

To find the tension in the rope, we calculate the moments caused by the counterweight and the projectile. The moment due to the stone is:

extClockwisemoment=610extkgimes9.81extm/s2imes1.5extm=8976extNm ext{Clockwise moment} = 610 ext{ kg} imes 9.81 ext{ m/s}^2 imes 1.5 ext{ m} = 8976 ext{ Nm}

And the moment due to the projectile is:

extAnticlockwisemoment=250extNimes4.0extm=1000extNm ext{Anticlockwise moment} = 250 ext{ N} imes 4.0 ext{ m} = 1000 ext{ Nm}

Setting the moments equal for static equilibrium, we can find the tension using the relation:

T=(89761000)extNm1.5extm=5310extNT = \frac{(8976 - 1000) ext{ Nm}}{1.5 ext{ m}} = 5310 ext{ N}

Step 3

04.1-3 Calculate the range.

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Answer

To calculate the range of the projectile, we first need to determine the time of flight. Using the height of release:

h=7.5extmh = 7.5 ext{ m}

Using the equation of motion for vertical drop:

t=2hg=2×7.59.811.23extst = \sqrt{\frac{2h}{g}} = \sqrt{\frac{2 \times 7.5}{9.81}} \approx 1.23 ext{ s}

Next, we calculate the horizontal distance (range) traveled during this time at a velocity of 18 m/s:

Range=vt=18extm/s×1.23exts22.14extm\text{Range} = v \cdot t = 18 ext{ m/s} \times 1.23 ext{ s} \approx 22.14 ext{ m}

Step 4

04.1-4 Discuss the effect this change has on the range of the catapult.

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Answer

If the projectile is released just before the wooden beam is vertical, it will have less time to travel horizontally due to an immediate downward acceleration rather than from a horizontal launch.

  1. Range may be smaller: The time spent in the air will decrease as the projectile will not have the same horizontal velocity component as when released horizontally.
  2. Counterweight dynamics: The counterweight will fall slower, allowing less height for the projectile, hence reducing distance.
  3. Conclusion: Overall, the range will be less than if released horizontally due to the decrease in horizontal velocity at the moment of release.

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