15 In this question, use \(g = 10 \mathrm {~m} \mathrm {~s} ^ { - 2 }\)
A box, B, of mass 4 kg lies at rest on a fixed rough horizontal shelf.
One end of a light string is connected to B .
The string passes over a smooth peg, attached to the end of the shelf.
The other end of the string is connected to particle, P , of mass 1 kg , which hangs freely below the shelf as shown in the diagram below.
\includegraphics[max width=\textwidth, alt={}, center]{1f887565-4587-4520-99d4-f3635b015525-22_778_910_760_566}
B is initially held at rest with the string taut.
B is then released.
B and P both move with constant acceleration \(a \mathrm {~ms} ^ { - 2 }\)
As B moves across the shelf it experiences a total resistance force of 5 N
15
- State one type of force that would be included in the total resistance force.
15
- Show that \(a = 1\)
15 - When B has moved forward exactly 20 cm the string breaks.
Find how much further B travels before coming to rest.
15 - State one assumption you have made when finding your solutions in parts (b) or (c). [1 mark]