Leonardo da Vinci (1452–1519) is creditedwith being the first to perform quantitative experiments on friction, though his results weren’t known until centuries later, due inpart to the secret code (mirror writing) he used in his notebooks.Leonardo would place a block of wood on an inclined plane andmeasure the angle at which the block begins to slide. He reportsthat the coefficient of static friction was 0.25 in his experiments.At what angle did Leonardo’s blocks begin to slide?

Two boxes (Box A = 9.7 kg and Box B = 5.4 kg) are connected by acord running over a pulley. The coefficient of kinetic friction betweenbox A and the table is 0.18. We ignore the mass of the cord and pulleyand any friction in the pulley, which means we can assume that a forceapplied to one end of the cord will have the same magnitude at theother end. We wish to find the tension of the cord while accelerating (inN), assuming the cord doesn’t stretch. As box B moves down, box Amoves to the right. Hint: Solve for the acceleration of the system first.

A 0.85 kg block of wood is stationary on an incline that is15◦above horizontal. A force of 3.0 N is being applied toit 75◦below horizontal, directly into the incline (the force isperpendicular to the incline). What is the minimum coefficientof static friction required to keep the block stationary?

A box of mass 5 kg is at rest on a rough plane inclined at an angle of 40° to the horizontal. Calculate the magnitude of the friction force, in newtons, to two significant figures. (Take the magnitude of the acceleration due to gravity, g. to be 9.8 ms 2.) The magnitude of the friction force is N (to 2.s.f.).

In the friction experiment, if the friction block has a mass of 599 g, and it started to move at a constant speed after giving it a slight push when the mass in the hanger is 284 g (including the hanger), what is the coefficient of kinetic friction?

inclined at an angle of 26.6º. Since the box is on wheels, assume that friction is negligable. A mover is pushing a 122 kg box up a ramp. The ramp is inclined at an 0 (A) Calculate the force the mover exerts to push the box up the ramp at a constant rate of 1.4 m/s. Assume he pushes parallel to the ramp. (B) Calculate the force the mover exerts to push the box up the ramp at a constant rate of 1.4 m/s². Assume he pushes parallel to the ramp. (C) Calculate the normal force the ramp exerts on the box. 1069.05 N 4.

A 70 kg bicyclist is riding her 15 kg bicycle downhill on a road with a slope of 80without pedaling or braking. The bicyclist has a frontal area of 0.45 m2and a dragcoefficient of 1.1 in the upright position, and a frontal area of 0.4 m2and a dragcoefficient of 0.9 in a racing position. If the downhill speed of the bicyclist(terminal velocity) can be determined when the total force acting on the “body” inthe direction of movement is equal to zero, determine the percentage of downspeed that she can be increased when she is in a racing position. Air temperatureis 150C and disregarding the rolling resistance and friction at the bearing.