2.
\begin{figure}[h]
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\caption{Fig. 1}
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Figure 1 shows a toy lorry being pulled by a piece of string, up a ramp inclined at an angle of \(25 ^ { \circ }\) to the horizontal. When the string is pulled with a force of 20 N parallel to the line of greatest slope of the ramp, the lorry is on the point of moving up the ramp.
In a simple model of the situation, the ramp is considered to be smooth.
- Draw a diagram showing all the forces acting on the lorry.
- Find the weight of the lorry and the magnitude of the reaction between the lorry and the ramp, giving your answers to an appropriate degree of accuracy.
- Write down any modelling assumptions that you have made about
- the lorry,
- the string.
In a more refined model, the ramp is assumed to be rough.
- State the effect that this would have on your answers to part (b).