PhysicsGrade 12en

⚙️ Newton's Laws and Free-Body Diagrams

Explore Newton's three laws of motion and master the construction and interpretation of free-body diagrams in complex scenarios. **What you'll learn:** - Apply Newton's three laws to predict motion and forces in systems - Construct accurate free-body diagrams for objects in equilibrium and acceleration - Resolve forces into components and calculate net force - Analyze tension, normal force, friction, and applied forces - Solve multi-body problems using Newton's second law

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Question 1
A book rests on a horizontal table. According to Newton's third law, what is the reaction force to the weight of the book?
Question 2
A car with mass $1500 \text{ kg}$ accelerates uniformly from rest over $8 \text{ s}$ to reach a velocity of $20 \text{ m/s}$ . The net force acting on the car is ___.
Question 3
An object moving at constant velocity in a straight line has a net force of zero acting on it.
Question 4
A box is being pulled across a rough horizontal floor by a rope at an angle of $30°$ above the horizontal. Which of the following correctly describes the effect of pulling at an angle rather than horizontally?
Question 5
Two blocks are in contact on a frictionless horizontal surface. Block A (mass $2 \text{ kg}$ ) is pushed by a $12 \text{ N}$ force to the right, and block B (mass $4 \text{ kg}$ ) is in contact with block A. What is the magnitude of the contact force (force that A exerts on B)?
Question 6
A block of mass $5 \text{ kg}$ hangs from a rope. If the rope can support a maximum tension of $75 \text{ N}$ , the maximum upward acceleration of the block is ___.
Question 7
A person stands in an elevator accelerating upward. How does the normal force on the person compare to their weight?
Question 8
An object is in equilibrium on an inclined plane. A student draws a free-body diagram with forces pointing downward (weight), perpendicular away from the plane (normal force), and parallel to the plane pointing up the slope (static friction). Is this diagram correct?
Question 9
Two objects are connected by a light string over a frictionless pulley. Object A (mass $3 \text{ kg}$ ) hangs vertically, and object B (mass $5 \text{ kg}$ ) also hangs vertically on the other side. When released, which statement is true?
Question 10
Arrange the following steps in the correct order to solve a Newton's second law problem involving an inclined plane: