Question 1

Paper 2Medium13 marks

A 16 kg16\ \mathrm{kg} sled moves horizontally along a level track. A rope pulls the sled through a displacement of 6.0 m6.0\ \mathrm{m} with a constant tension of 50 N50\ \mathrm{N} at 35∘35^\circ above the horizontal. A constant friction force of 18 N18\ \mathrm{N} acts opposite to the motion. The sled’s initial speed is 1.0 m s−11.0\ \mathrm{m\,s^{-1}} Ignore air resistance.

(a)

Calculate the work done on the sled by the tension in the rope.

[2]
(b)

Calculate the work done on the sled by friction.

[2]
(c)

Determine the work done by the resultant force on the sled over the displacement.

[2]
(d)

Determine the sled’s speed after it has moved through 6.0 m6.0\ \mathrm{m}

[3]
(e)

Account for the difference between the work done by the rope and the increase in the sled’s kinetic energy.

[2]
(f)

In a repeat run, the rope is at 50∘50^\circ above the horizontal. The tension, displacement, initial speed and friction force are unchanged. Calculate the work done by the rope and deduce whether the sled’s final speed is greater or smaller than in the first run.

[2]

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