Test on Inclined plane and friction
Inclined Plane and Friction: Comprehensive Guide for Students
Test: Skloněná rovina s třením
20 questions
Question 1: The force perpendicular to an object on an inclined plane is always equal to the object's total weight (m · g).
A. Yes
B. No
Explanation: On an inclined plane, the force perpendicular to the incline (F⊥) is calculated as F⊥ = m · g · cos θ. This component of gravity is equal in magnitude to the normal force (N), which is N = m · g · cos θ. The normal force, and thus the perpendicular component of gravity, is only equal to the object's total weight (m · g) when the plane is horizontal (θ = 0°). This is specifically noted as a common misconception in the study materials.
Question 2: In the worked example, the normal force acting on the 2.0 kg wooden block on the 30-degree inclined plane is equal to its full weight of 19.62 N.
A. Yes
B. No
Explanation: The study materials explicitly state that on an inclined plane, the normal force is equal to the perpendicular component of the gravitational force, not the full weight. In the worked example, the normal force was calculated as 17.00 N, which is the perpendicular component (F⊥), while the full gravitational force (weight) was 19.62 N. The normal force is N = m · g · cos θ, not m · g.
Question 3: As the angle of inclination of an inclined plane increases, the normal force acting on an object resting on it increases.
A. Yes
B. No
Explanation: The study materials state that as the angle of inclination (θ) increases, the cosine of the angle (cos θ) decreases. Since the normal force (N) is calculated as N = m · g · cos θ, a decrease in cos θ directly leads to a decrease in the normal force. Therefore, an increasing angle of inclination causes the normal force to decrease, not increase.
Question 4: In the worked example provided, the gravitational force (weight) for the 2.0 kg wooden block was calculated to be 19.62 N.
A. Yes
B. No
Explanation: According to 'Step 1: Calculate the gravitational force (weight)' in the worked example, the gravitational force is calculated as *F_g* = *m* · *g* = 2.0 kg · 9.81 m/s² = 19.62 N. Therefore, the statement is correct.
Question 5: The formula for the acceleration of an object sliding down an inclined plane with kinetic friction includes the product of the gravitational acceleration and the difference between the sine of the incline angle and the product of the coefficient of kinetic friction and the cosine of the incline angle.
A. Yes
B. No
Explanation: The study materials state the formula for acceleration as *a* = *g* · (sin *θ* - *μk* · cos *θ*). This matches the description, showing the acceleration is equal to the gravitational acceleration (*g*) multiplied by (sin *θ* - *μk* · cos *θ*), which is the difference between the sine of the incline angle (sin *θ*) and the product of the coefficient of kinetic friction (*μk*) and the cosine of the incline angle (cos *θ*).