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A trolley of mass 1,5 kg is held stationary at point A at the top of a frictionless track - NSC Physical Sciences - Question 4 - 2018 - Paper 1

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A trolley of mass 1,5 kg is held stationary at point A at the top of a frictionless track. When the 1,5 kg trolley is released, it moves down the track. It passes po... show full transcript

Worked Solution & Example Answer:A trolley of mass 1,5 kg is held stationary at point A at the top of a frictionless track - NSC Physical Sciences - Question 4 - 2018 - Paper 1

Step 1

4.1 Use the principle of conservation of mechanical energy to calculate the speed of the 1,5 kg trolley at point P.

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Answer

To calculate the speed of the 1,5 kg trolley at point P, we can apply the principle of conservation of mechanical energy:

At point A, the potential energy (PE) of the trolley is given by: PEA=mimesgimesh=1.5imes9.81imes2.0PE_A = m imes g imes h = 1.5 imes 9.81 imes 2.0 While at point P, all of this potential energy is converted into kinetic energy (KE): KEP=12mv2KE_P = \frac{1}{2} m v^2 Setting the potential energy at point A equal to the kinetic energy at point P: mgh=12mv2mgh = \frac{1}{2} mv^2

Cancelling mass (m) from both sides: gh=12v2gh = \frac{1}{2} v^2

Rearranging to solve for v, we have: v=2gh=2imes9.81imes2.0v = \sqrt{2gh} = \sqrt{2 imes 9.81 imes 2.0} This results in: v \approx 6.26 , \text{m/s}

Step 2

4.2 The principle of conservation of linear momentum is given by the incomplete statement below.

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The complete statement filling in the missing word is:

"In an isolated system, the total linear momentum is conserved."

Step 3

4.3 Calculate the speed of the combined trolleys immediately after the collision.

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Using the conservation of momentum before and after the collision:

Let: m1 = 1.5 kg (mass of the first trolley), m2 = 2.0 kg (mass of the second trolley), v1 = 6.26 m/s (initial speed of the first trolley), v2 = 0 m/s (initial speed of the second trolley).

Momentum before collision: pinitial=m1v1+m2v2=1.5imes6.26+2.0imes0=9.39kg m/sp_{initial} = m_1 v_1 + m_2 v_2 = 1.5 imes 6.26 + 2.0 imes 0 = 9.39 \, \text{kg m/s}

After the collision, the two trolleys stick together: Let (v_f) be their final speed: pfinal=(m1+m2)vf=(1.5+2.0)vfp_{final} = (m_1 + m_2) v_f = (1.5 + 2.0) v_f

Setting initial momentum equal to final momentum: 9.39=(1.5+2.0)vf9.39 = (1.5 + 2.0) v_f

Solving for (v_f): vf=9.393.52.68 m/sv_f = \frac{9.39}{3.5} \approx 2.68 \text{ m/s}

Step 4

4.4 Calculate the distance travelled by the combined trolleys in 3 s after the collision.

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Answer

Using the formula for distance travelled:

Δx=vft+12at2\Delta x = v_f t + \frac{1}{2} a t^2

Since there is no acceleration following the inelastic collision (they move together at constant speed):

  1. The initial speed after collision (v_f = 2.68 , \text{m/s})
  2. The acceleration (a = 0)

Substituting 3 seconds for (t): Δx=2.68imes3+12×0imes32\Delta x = 2.68 imes 3 + \frac{1}{2} \times 0 imes 3^2 Δx=8.04m\Delta x = 8.04 \, \text{m}

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