1) Helicopter blades withstand tremendous stresses. In addition to supporting the weight of a helicopter, they are spun at rapid rates and experience large centripetal accelerations, especially at the tip. (For each answer, enter a number.)

(a)Compare the linear speed of the tip with the speed of sound (taken to be 340 m/s).

v_tip/v_sound =

2)

A contestant in a winter games event pushes a 58.0 kg block of ice across a frozen lake as shown in the figure below. The coefficient of static friction is 0.1 and the coefficient of kinetic friction is 0.03. (For each answer, enter a number.) (a) Calculate the minimum force F (in N) he must exert to get the block moving. N (b) What is its acceleration (in m/s ) once it starts to move, if that force is maintained? m/s2