A block of mass m = 2.40 kg is pushed a distance d = 2.40 m along a frictionless

Question

A block of mass m = 2.40 kg is pushed a distance d = 2.40 m along a frictionless, horizontal table by a constant applied force of magnitude F = 16.0 N directed at an angle = 20.0° below the horizontal as shown in the figure below.

(a) Determine the work done on the block by the applied force.
J

(b) Determine the work done on the block by the normal force exerted by the table.
J

(c) Determine the work done on the block by the gravitational force.
J

(d) Determine the work done by the net force on the block.
J

Explanation / Answer

The definition of work in this instance is W=F(dot)d, where F is the force applied and d the distance travelled by means of said force. Since the block is moving horizontally, and not vertically, we can discount the vertical component of the applied force and deal only with the horizontal component.

a) Since F is 20deg below the horizontal, the horizontal component of the force is F*cos(20)=16*0.94= 15.04

The block travels 2.4m, so W=2.4*15.04 = 36.10 N.

b) Normal force is always perpendicular to the surface, which is in this case horizontal; this means the normal force is perfectly vertical. This means that there is no horizontal component of the force to affect the block's motion, so W=0N.

c) Similar to the normal force, the gravitational force is vertical, so W=0N.

d) Since gravity, the normal force, and the vertical component of the applied force cancel out vertically, the net force on the block is the horizontal component of the applied force. Thus, the net force on the block must, therefore, be the same as part a). The distance travelled does not change, so W miust also be the same.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

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