Newton's Laws of Motion
Fill in the blank: An object at rest will remain at ____________________, and an object in motion will continue moving at a constant ____________________, unless acted on by an unbalanced force.
rest; velocity
DEFINITION: Explain what a free body diagram is and why it is useful in Physics.
A simplified representation used in physics to show all the forces acting on a single object or "body." In an FBD, the object is typically represented as a dot or a simple shape, and all the forces acting on it are shown as arrows pointing in the direction of each force. Each arrow is labeled with the type of force (e.g., gravitational force, normal force, frictional force) and often the magnitude of the force if known
Types of Contact Forces (Basic Matching)
Match each contact force with its correct description by writing the letter in the blank next to each force.
Friction __________
Normal Force __________
Tension __________
a) Force acting to support objects on a surface, perpendicular to the surface.
b) A resistive force acting opposite to motion between two surfaces in contact.
c) A pulling force transmitted through a string, rope, or cable.
b, a, c
Fill in the formula for calculating force.
__________ = __________ x __________
F = m x a
Definition: What is net force?
The total force acting on an object when all individual forces are combined. It is the vector sum of all the forces acting on that object, taking into account both their magnitudes and directions. The net force determines the object’s acceleration and motion according to Newton's second law of motion
Fill in the blank: For every action, there is an equal and ____________________ reaction
opposite
A box weighing 50 N is resting on a flat surface. A person pushes the box to the right with a force of 20 N, while friction between the box and the surface provides a resistance force of 10 N to the left. Draw the Free Body Diagram for this box.
Gravitation force acting down, normal force acting up, applied force acting to the right, friction force acting to the left
Types of Non-Contact Forces (Basic Matching)
Match each non-contact force with its correct description by writing the letter in the blank next to each force.
Gravity __________
Applied Force __________
Air Resistance __________
a) A force exerted by a person or object that is pushing or pulling on another object.
b) A force that pulls objects toward the center of the Earth due to their mass.
c) A force that opposes the motion of an object as it moves through the air.
b, a, c
A 10 kg object accelerates at 1.5 m/s². What is the force acting on it?
F = 15 N
1. TRUE or FALSE: If forces are balanced, the object is stationary.
2. TRUE or FALSE: If forces are unbalanced, the object is moving at a changing rate of velocity.
3. TRUE or FALSE: If forces are balanced, the object is moving at a constant velocity.
1. FALSE
2. TRUE
3. TRUE
What is the formula for calculating force according to Newton’s Second Law?
Formula: F= __________x__________
F = m x a
For each of the following scenarios, identify the type of force acting on the object. Choose from: Normal Force, Weight/Gravity, Friction, Tension, or Applied Force.
A box pushed across the floor: ____________________ and ____________________.
A person hanging from a rope: ____________________ and ____________________.
2. tension; weight/gravity
True or False: The normal force always acts in the direction of motion for objects on a surface.
True or False: Tension in a rope is always a pulling force, not a pushing force.
False
True
An object experiences a force of 50 N and has a mass of 5 kg. What is its acceleration?
a = 10 m/s2
An object has a force of 20 N acting to the right and a force of 10 N acting to the left. What is the net force? Show your work.
20 N right - 10 N left = 10 N right
You are waiting in line to use the diving board at your local pool. While watching people dive into the pool from the board, you realize that using a diving board to spring into the air before a dive is a good example of Newton’s third law of motion. Explain how a diving board illustrates Newton’s third law of motion.
When a diver pushes down on the diving board, they exert a force on it. According to Newton’s third law, the diving board exerts an equal and opposite force upward on the diver. This upward force propels the diver into the air, allowing them to dive.
Draw a free body diagram of a bicyclist riding down the road at a constant velocity.
Gravity (Weight): Draw a downward arrow from the center of the cyclist labeled Fg.
Normal Force: Draw an upward arrow from the same point labeled Fn, equal in length to the gravitational force arrow.
Applied Force: Draw a horizontal arrow to the right (direction of motion) labeled Fa.
Friction/Air Resistance: Draw a horizontal arrow to the left labeled Ff or Fd, equal in length to the applied force arrow.
A book rests on a table. Identify all the forces acting on the book and explain why it remains at rest. Be sure to include gravity, normal force, and any other relevant forces.
A car experiences a force of 1200 N when it accelerates at a rate of 4 m/s². What is the mass of the car?
m = 300 kg
How can you determine if forces are balanced or unbalanced based on the free body diagrams that are given?
A FBD will be balanced if all the arrows (forces) are the same length and a FBD will be unbalanced if all the arrows are not the same length
Calculation: If an object accelerates at 22 m/s² with a force of 50 N, what is the mass of the object?
MAKE SURE TO SHOW ALL THE STEPS!!!
1. Identify the variables (F, m, a)
2. Identify formula
3. Input and Solve
4. Answer with units and direction (if vector)
1. F = 50 N, m = ?, a = 22 m/s2
2. m = F/a
3. m = (50 N)/(22 m/s2)
4. m = 2.27 kg
What force is responsible for slowing down the bicyclist riding down the road at a constant velocity?
A car accelerates forward on a flat road. Identify and explain the roles of at least four different types of forces acting on the car (e.g., friction, normal force, gravity, applied force). Discuss how these forces contribute to the car’s motion and how they interact with each other as the car accelerates.
Applied Force: This is the forward force provided by the car’s engine, transmitted to the road through the wheels.
Friction (specifically static friction): Friction between the tires and the road prevents the tires from slipping and provides the necessary grip to move forward. This frictional force actually helps propel the car forward.
Normal Force: This force acts upward, exerted by the road on the car, balancing the car's weight vertically.
Gravity: Gravity pulls the car downward due to its mass, which is balanced by the normal force.
As the car accelerates, the applied force (from the engine) overcomes air resistance and rolling resistance. Friction helps in forward motion without slipping, while the normal and gravitational forces remain balanced vertically, ensuring the car stays on the road.
Explanation: Explain how changing the mass of an object affects the force needed to accelerate it at the same rate. Will the force needed increase or decrease?
Changing the mass of an object affects the force needed to accelerate it at the same rate due to Newton's second law of motion, which states that F=m×a. If the mass increases while the desired acceleration remains constant, the force required must also increase. Conversely, if the mass decreases, the force needed will decrease.
A person pushes a 3 kg box with a force of 15 N to the right, while a 4 N frictional force acts to the left.
1. Calculate the net force on the box.
2. Then use Newton’s Second Law to find the box's acceleration.
2. a = F/m
a = (11 N)/(3 kg) = 3.67 m/s2