A block of mass m=353g is dragged with a string across a rough horizontal table.

Question

A block of mass m=353g is dragged with a string across a rough horizontal table.  The string tension is T = 3.75N and it pulls upward at an angle of 44 degrees with the horizontal.  At one particular instant the block is moving a speed of v=6.5m/s.  The coefficient of kinetic friction is between the block and the table is u=0.624

What is the power supplied to the block by the string _____W

What is the power supplied by the force friction _______W

At this instant the block's speed is 1 decreasing, 2 constant, 3 increasing, 4 impossible to tell

Explanation / Answer

frictional force f = mue*(m*g - T*sin(44))

f = 0.624*(0.353*9.8 - 3.75*sin(44))

f = 0.5375 N

Fx = T*cos(44) = 3.75*cos(44) = 2.698 N

P(string) = T*cos(44)*v*cos(0) = 17.53 watts

P(friction) = f*v*cos(180) = -3.5 watts

here Fx is greate than f, so the block speed increases.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.