Question

You have constructed a raft that is 2.00 m long, 2.00 m wide, and 0.100 m thick. Part A If the mass of the raft is 20.0 kg and your mass is 55.0 kg, how many 65.0 kg friends can cross a river with you during one trip

Answer 1

Answer:

5

Explanation:

Volume of raft, $v_r= 2\times 2\times 0.1= 0.4 m^{3}$

Density of raft, $\rho_r=\frac {m_r}{v_r}=\frac {20}{0.4}=50 Kg/m^{3}$

Total weight= Buoyant force

Assuming n number of friends weighing 65 Kg then

(20+55+65n)g= Buoyant force

Buoyant force will be given by multiplying density of water by volume by acceleration due to gravity

$(75+65n)g=0.4m^{3}\times 1000 Kg/m^{3}\times g$

g is on both sides so they cancel

75+65n=400

65n=400-75=325

$n=\frac {325}{65}=5$

Therefore, 5 friends each weighing maximum of 65 Kg can go with you on one trip