7. A sledge of mass 78 kg is pulled up a slope by means of a rope. The slope is modelled as a rough plane inclined at an angle \(\alpha\) to the horizontal, where \(\tan \alpha = \frac { 5 } { 12 }\). The rope is modelled as light and inextensible and is in a line of greatest slope of the plane. The coefficient of friction between the sledge and the slope is 0.25 . Given that the sledge is accelerating up the slope with acceleration \(0.5 \mathrm {~m} \mathrm {~s} ^ { - 2 }\),
- find the tension in the rope.
The rope suddenly breaks. Subsequently the sledge comes to instantaneous rest and then starts sliding down the slope.
- Find the acceleration of the sledge down the slope after it has come to instantaneous rest.
(6 marks)
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