4. A tent peg is driven into soft ground by a blow from a hammer. The tent peg has mass 0.2 kg and the hammer has mass 3 kg . The hammer strikes the peg vertically. Immediately before the impact, the speed of the hammer is \(16 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). It is assumed that, immediately after the impact, the hammer and the peg move together vertically downwards.

1. Find the common speed of the peg and the hammer immediately after the impact. Until the peg and hammer come to rest, the resistance exerted by the ground is assumed to be constant and of magnitude \(R\) newtons. The hammer and peg are brought to rest 0.05 s after the impact.
2. Find, to 3 significant figures, the value of \(R\).