Passage
Laparoscopy is a minimally invasive surgical procedure where small surgical instruments are inserted into the body through cannulas (hollow tubes 0.5 to 1.0 cm in diameter) . A cannula is inserted into the skin while sleeved around a trocar (Figure 1) . The skin incision can be made directly with a sharp-tipped trocar as it is being inserted with the cannula. If a blunt-tipped trocar is used, the incision is made beforehand with a surgical blade. After insertion, the trocar is removed, leaving the cannula as an access point for laparoscopic procedures.
Figure 1 Cannula, trocar, and two types of tipsLow-friction trocars increase surgical precision and reduce postoperative scarring. Friction between the skin and trocar tip is tested with synthetic skin and a stationary ramp whose surface is made of the same material as the trocar. For testing, the synthetic skin is pressed against the ramp's surface by a load, weighted to allow the skin to slide down at a constant speed (Figure 2) . In this setup, the weight of the synthetic skin layer is negligible.
Figure 2 Experimental setup to test the friction between trocar and skin
Adapted from W. Firme-Gustavo et al., (C) 2015 Society of Laparoendoscopic Surgeons.
-In the experiment, the magnitude of the kinetic frictional force between the ramp and the synthetic skin depends on:the area of the contact surface.the mass of the load.the speed of the synthetic skin.

Question

Passage
Laparoscopy is a minimally invasive surgical procedure where small surgical instruments are inserted into the body through cannulas (hollow tubes 0.5 to 1.0 cm in diameter) . A cannula is inserted into the skin while sleeved around a trocar (Figure 1) . The skin incision can be made directly with a sharp-tipped trocar as it is being inserted with the cannula. If a blunt-tipped trocar is used, the incision is made beforehand with a surgical blade. After insertion, the trocar is removed, leaving the cannula as an access point for laparoscopic procedures.

Figure 1 Cannula, trocar, and two types of tipsLow-friction trocars increase surgical precision and reduce postoperative scarring. Friction between the skin and trocar tip is tested with synthetic skin and a stationary ramp whose surface is made of the same material as the trocar. For testing, the synthetic skin is pressed against the ramp's surface by a load, weighted to allow the skin to slide down at a constant speed (Figure 2) . In this setup, the weight of the synthetic skin layer is negligible.

Figure 2 Experimental setup to test the friction between trocar and skin
Adapted from W. Firme-Gustavo et al., (C) 2015 Society of Laparoendoscopic Surgeons.
-In the experiment, the magnitude of the kinetic frictional force between the ramp and the synthetic skin depends on:the area of the contact surface.the mass of the load.the speed of the synthetic skin.

Quizplus · Accepted Answer

11ecba2d_12f1_bdc2_a3bf_df4427676eb6_MD0008_00 Kinetic friction is the frictional force between two sliding surfaces, and it is the product of the coefficient of kinetic friction μ_k (specific to the two surfaces) and the normal force N (perpendicular force a surface exerts on another): 11ecba2d_12f1_bdc3_a3bf_cd26cbf93c1b_MD0008_00 Therefore, the magnitude of the frictional force is proportional to N. In the case of the experiment described in the passage, the synthetic skin is resting on a ramp (Figure 2), and therefore the load's weight determines N. Because weight is proportional to mass (W = mg), the mass of the load determines the magnitude of kinetic friction in the experiment (Number II). (Number I) Friction is determined by the normal force between two surfaces, which is independent of the area of the contact surface; contact areas of unequal size that experience the same normal force will experience the same amount of friction. Therefore, friction is independent of surface area. (Number III) Because the value of the coefficient of kinetic friction μ_k depends only on the properties of the two surfaces, the magnitude of kinetic friction is independent of speed. Educational objective: The mass of an object determines its weight, which determines the normal force of an object sliding on a surface. Because kinetic friction is proportional to the normal force (F_k = μ_kN), kinetic friction depends on an object's mass. The coefficient of kinetic friction μ_k is independent of the size of the contact surface and the speed between the surfaces.

Passage Laparoscopy Is a Minimally Invasive Surgical Procedure Where Small Surgical