Podcast
Questions and Answers
What is not a force?
What is not a force?
- Friction
- Gravity
- Momentum (correct)
- Weight
You push on the box and are unable to move it. What force opposes your push?
You push on the box and are unable to move it. What force opposes your push?
- Rolling friction
- Static friction (correct)
- Sliding friction
- Air resistance
Air resistance depends on _____
Air resistance depends on _____
- The velocity of a moving object (correct)
- The inertia of a moving object
- The weight of a moving object
- The mass of a moving object
What force besides gravity acts on a projectile?
What force besides gravity acts on a projectile?
Newton's first law of motion is sometimes called the law of _____.
Newton's first law of motion is sometimes called the law of _____.
A change in which of the following affects the weight of an object?
A change in which of the following affects the weight of an object?
Which represents Newton's second law?
Which represents Newton's second law?
Complete the sentence. For every action there is a _____
Complete the sentence. For every action there is a _____
Momentum depends upon _____
Momentum depends upon _____
What force holds the nucleus together?
What force holds the nucleus together?
Suppose two 4 Newton forces act on an object in the same direction. What is the net force on the object?
Suppose two 4 Newton forces act on an object in the same direction. What is the net force on the object?
Five different forces act on an object. Is it possible for the net force on the object to be 0? Explain.
Five different forces act on an object. Is it possible for the net force on the object to be 0? Explain.
What happens to an object when an unbalanced force acts on it?
What happens to an object when an unbalanced force acts on it?
You push harder and harder on a box until it began sliding across the floor. Which was the stronger of the forces acting on the block: static friction or sliding friction?
You push harder and harder on a box until it began sliding across the floor. Which was the stronger of the forces acting on the block: static friction or sliding friction?
Explain why a falling object subjected to Earth's gravity does not continue to accelerate forever.
Explain why a falling object subjected to Earth's gravity does not continue to accelerate forever.
What is the difference between mass and weight?
What is the difference between mass and weight?
What is an action-reaction pair?
What is an action-reaction pair?
What must you know to determine which of two vehicles traveling at the same velocity has the greater momentum?
What must you know to determine which of two vehicles traveling at the same velocity has the greater momentum?
What force is responsible for your socks sticking together after they've been in a clothes dryer?
What force is responsible for your socks sticking together after they've been in a clothes dryer?
What particles do the strong and weak nuclear forces act on?
What particles do the strong and weak nuclear forces act on?
What force is responsible for the orbits of the planets in the solar system?
What force is responsible for the orbits of the planets in the solar system?
When shooting an arrow at the target, why is it advisable to aim above the target rather than directly at it?
When shooting an arrow at the target, why is it advisable to aim above the target rather than directly at it?
The moon's gravity is only one sixth that of Earth. Explain how the weight of an object differs between the two locations.
The moon's gravity is only one sixth that of Earth. Explain how the weight of an object differs between the two locations.
When a tennis player practices by hitting the ball against the wall, which of Newton's laws of motion is the player making use of?
When a tennis player practices by hitting the ball against the wall, which of Newton's laws of motion is the player making use of?
Consider two rocks with masses of 1 and 10 kilograms. What is the relation between their inertias, masses, and weights?
Consider two rocks with masses of 1 and 10 kilograms. What is the relation between their inertias, masses, and weights?
On Earth during the fuel economy test of a sports car, why does the car achieve more miles per gallon of gasoline when its convertible top is down?
On Earth during the fuel economy test of a sports car, why does the car achieve more miles per gallon of gasoline when its convertible top is down?
What are the two ways in which the acceleration of an object can be increased?
What are the two ways in which the acceleration of an object can be increased?
A 100 kilogram crate sliding on the floor is brought to a stop by a 25 Newton force. What is the deceleration of the crate?
A 100 kilogram crate sliding on the floor is brought to a stop by a 25 Newton force. What is the deceleration of the crate?
What is the momentum of an 80 kilogram runner moving at the speed of 2.5 m/s?
What is the momentum of an 80 kilogram runner moving at the speed of 2.5 m/s?
What is the weight on Earth of a girl with a mass of 30 kilograms? The acceleration due to gravity on Earth is 9.8 meters per second squared.
What is the weight on Earth of a girl with a mass of 30 kilograms? The acceleration due to gravity on Earth is 9.8 meters per second squared.
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Study Notes
Forces and Motion
- Momentum is not a force; it is dependent on mass and velocity.
- Static friction opposes the initial push on an object, preventing its movement.
- Air resistance increases with the velocity of a moving object, impacting its motion.
- Besides gravity, air resistance is a significant force acting on projectiles.
Newton's Laws of Motion
- Newton's first law is known as the law of inertia, describing an object's resistance to changes in motion.
- Newton's second law is represented as a = F/m, correlating acceleration with force and mass.
- According to Newton's third law, for every action there is an equal and opposite reaction.
Weight and Gravity
- Weight changes based on the acceleration due to gravity; mass remains constant regardless of location.
- The moon’s gravity is one-sixth that of Earth, making weights different while masses stay the same.
Characteristics of Forces
- The net force is the overall force acting on an object, and multiple forces can cancel to create a net force of zero.
- Forces acting in the same direction are additive; two 4 Newton forces give a net force of 8 Newtons.
Projectile Motion
- A projectile follows a curved path due to gravity, requiring adjustments in aim when targeting.
Practical Applications of Forces
- The strong nuclear force holds protons and neutrons together in atomic nuclei.
- Gravitational force keeps planets in orbit, essential for the stability of the solar system.
Miscellaneous Concepts
- Electric force can cause objects like socks to stick together.
- The inertia of an object is directly proportional to its mass; a 10 kg object exhibits ten times the inertia of a 1 kg object.
- Air resistance influences fuel economy in vehicles, affecting performance based on their aerodynamic shape.
Acceleration Factors
- An object's acceleration can be increased by either applying more force or reducing its mass.
- Deceleration can be calculated; for example, a 100 kg crate decelerating under a 25 Newton force results in 0.25 m/s².
Calculations
- The momentum of an object is calculated using its mass and velocity, e.g., an 80 kg runner at 2.5 m/s has a momentum of 200 kg m/s.
- The weight of an object is calculated by multiplying its mass by the acceleration due to gravity, e.g., a girl with a mass of 30 kg weighs approximately 290 N on Earth (30 kg × 9.8 m/s²).
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