PhysicsGrade 12en

⚡ Newton's Laws and Free-Body Diagrams

Master the application of Newton's three laws of motion and the construction of free-body diagrams to solve complex force problems. **What you'll learn:** - Apply Newton's first, second, and third laws to predict motion and equilibrium - Construct accurate free-body diagrams for objects under multiple forces - Resolve forces into components and calculate net force - Distinguish between static and kinetic friction in real-world scenarios - Solve multi-body problems involving tension, normal forces, and applied forces

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Question 1
A book rests on a horizontal table. Which of the following correctly describes the forces acting on the book using Newton's third law?
Question 2
An object moving at constant velocity in a straight line must have a net force of zero acting upon it.
Question 3
Newton's second law states that the net force on an object equals ___, which can be written as the equation $F_{net} = ma$ .
Question 4
A 5.0 kg block is pulled across a horizontal surface by a rope at an angle of $30°$ above the horizontal. The applied force in the rope is 20 N. Assuming the coefficient of kinetic friction is 0.15 and $g = 10 \ \text{m/s}^2$ , what is the magnitude of the normal force?
Question 5
When drawing a free-body diagram, action–reaction pairs should both be included on the same diagram for the object being analyzed.
Question 6
Two blocks are in contact on a frictionless horizontal surface. Block A (mass $m_A = 3 \ \text{kg}$ ) is pushed by a force of 12 N, and block B (mass $m_B = 2 \ \text{kg}$ ) is in contact behind it. The acceleration of the system is ___ $\text{m/s}^2$ , and the contact force between the blocks is ___ N.
Question 7
A 2.0 kg block hangs from a rope attached to the ceiling. The rope has a breaking strength of 30 N. If the block is pulled upward with an acceleration of $5.0 \ \text{m/s}^2$ , what is the tension in the rope? (Use $g = 10 \ \text{m/s}^2$ .)
Question 8
A car moving around a flat circular track at constant speed experiences zero acceleration because its speed is not changing.
Question 9
Arrange the following steps in the correct order for solving a Newton's second law problem with multiple forces:
Question 10
An elevator accelerates upward at $2.0 \ \text{m/s}^2$ . A 60 kg passenger stands on a scale inside the elevator. What does the scale read? (Use $g = 10 \ \text{m/s}^2$ .)