Rider Canoe
if you can answer any of the physics problems?
1) a 2.5 kg block is held against a compressed horizontal spring. The spring has a force constant of k=15.1 N/m ans is compressed (again, horizontally) a distance of 1.3m. the block is released. Because of friction with the table top, the block comes to rest after traveling 5.1m from the point where it lost contact with the spring. What is the coefficient of kinetic friction between the block and the floor?
2)Two canoes are tied together and traveling down a river with the current. Spotting a waterfall, the two canoeists cut the rope and push off of each other to try and reach opposite banks of the river. They are in the middle of the river and will reach the waterfall in 4s. One canoe and its rider have a combined mass of 85kg and reach the shore in 3.4s. The other canoe and rider reach the opposite shore just in time at 3.9s. What is the combined mass of this canoe and riders?
Energy in the spring = 1/2 . 15.1 . 1.3^2 = 12.76 J
Starting speed of block when leaving the spring is given by 1/2 . m . v^2 = 12.76
v^2 = 10.2
v = 3.2 m/s
deceleration = 3.2^2 / 2 . d = 1 m/s/s
Force = m . a = 2.5 . 1 = 2.5 N
Friction force = µ . m . g = 2.5
µ = 2.5 / 2.5 . 9.8 = 0.10
2) Momentum sideways is zero to start with and must be conserved
Velocity sideways is inversely proportional to the time taken to reach the shore.
85 . 1/3.4 = M . 1/3.9
M = 97.5
Combined mass is 182.5 kg
NO HORSE NO RIDER – Boy and a Girl in a Little Canoe