Bob, who has a mass of 76 kg, can throw a .510 g rock with a speed of 31 m/s. Th
ID: 1607497 • Letter: B
Question
Bob, who has a mass of 76 kg, can throw a .510 g rock with a speed of 31 m/s. The distance through which his hand moves as he accelerates the rock forward from rest until he releases it is 1.0 m. What constant force must Bob exert on the rock to throw it with this speed? Express your answer to two significant figures and include the appropria If Bob s standing on frictionless ice, what is his recoil speed after releasing the Express your answer to two significant figures and include the appropriateExplanation / Answer
from the equation
v^2 = u^2+2ax
a = v^2/2x = 31^2/2*1 = 480.5 m/s^2
from the newton's second law
f = ma
f = 0.51*480.5 = 245.05 N
b) from the conservation of momentum
0 = 76*v+0.51*31
v = -0.208 m/s