Physics Chapter on Mass and Momentum

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Questions and Answers

What is the primary characteristic of mass?

It has a direction in space.

It measures the amount of matter in a body. (correct)

It is measured in newtons.

It is a vector quantity.

What is the SI unit of mass?

Kilogram (correct)

Newton

Gram

Pound

How is momentum calculated?

p = mass + velocity

p = mass × velocity (correct)

p = mass - velocity

p = mass / velocity

If a 70 kg skateboarder moves west at 4 m/s, what is his momentum?

280 kg·m/s west Signup and view all the answers

What does the conservation of momentum state in a closed system?

Total momentum before equals total momentum after. Signup and view all the answers

Which physical principle describes the behavior of a spacecraft accelerating by expelling gas?

Newton's Third Law Signup and view all the answers

What type of collision is commonly used to demonstrate the conservation of momentum in physics?

Direct (head-on) impacts Signup and view all the answers

What is the relationship between velocity and directional momentum?

Momentum direction is dependent on velocity and mass. Signup and view all the answers

What is the relationship between force and acceleration in a system?

Force is proportional to acceleration. Signup and view all the answers

What must be kept constant to ensure that changes in acceleration are due solely to the applied force?

The mass of the trolleys. Signup and view all the answers

How is acceleration due to gravity calculated in the described experiment?

By squaring the time and plotting against distance. Signup and view all the answers

What is the primary purpose of using a dense metal sphere in the experiment?

To minimize air resistance. Signup and view all the answers

What principle is demonstrated by the collision between two spheres in the experiment?

The principle of conservation of momentum. Signup and view all the answers

What adjustment is important for ensuring constant velocity in the trolley experiment?

Maintaining a slight slope. Signup and view all the answers

When conducting the momentum experiment, what happens to trolley A after the collision?

It comes to rest. Signup and view all the answers

How can the accuracy of the trolley experiment be improved?

Oiling the trolley wheels. Signup and view all the answers

What happens to the net force when the total forces acting on an object are balanced?

Net force equals zero. Signup and view all the answers

What mathematical relationship describes the acceleration of a body under the action of force?

F = ma Signup and view all the answers

For the experiment measuring the distance from the sphere to the trapdoor, what is crucial for precision?

Avoiding parallax errors. Signup and view all the answers

Why should external forces be minimized during the experiment with the falling sphere?

To maintain consistent results. Signup and view all the answers

What type of graph is used to analyze the relationship between distance and time squared?

Line graph. Signup and view all the answers

What forces must be measured to calculate the net force on the golfer's trolley?

Frictional force, weight, and applied force. Signup and view all the answers

What is the primary reason objects of different masses fall at the same rate in a vacuum?

Air resistance is negligible Signup and view all the answers

How is weight defined in relation to an object's mass?

Weight is mass multiplied by the acceleration due to gravity Signup and view all the answers

What two forces must be balanced for a skydiver to reach terminal velocity?

Weight and air resistance Signup and view all the answers

What key factor affects the acceleration due to gravity (g) at different altitudes on Earth?

The planet's mass and distance from its center Signup and view all the answers

Which statement about friction is false?

Friction depends only on the weight of the object Signup and view all the answers

What is the net force acting on a 30 kg block being pulled with an applied force of 250 N, with a frictional force of 70 N?

180 N Signup and view all the answers

What must be true about the forces acting on an object at rest on a flat surface?

The object experiences an upward force equal to the gravitational force Signup and view all the answers

To maintain constant velocity while traveling uphill, the force generated must overcome which opposing forces?

Frictional force and the gravitational pull down the incline Signup and view all the answers

What does the gravitational force on Earth depend on?

Total mass and radius of the Earth Signup and view all the answers

What is indicated by the term 'terminal velocity'?

The speed at which two opposing forces are balanced Signup and view all the answers

When conducting an experiment, how should mass and weight be differentiated?

Mass is constant, while weight varies with gravity Signup and view all the answers

What role does a lubricant play in the context of friction?

It reduces friction by separating surfaces Signup and view all the answers

What is the relationship between acceleration due to gravity and distance from the Earth's center?

It decreases with the square of the distance from the center Signup and view all the answers

What is the velocity of the yellow puck after the collision?

3 m/s to the right Signup and view all the answers

What is the combined speed of the skier and snowboarder after the collision?

4 m/s Signup and view all the answers

Which of the following correctly defines a newton?

The force needed to accelerate a 1 kg mass by 1 m/s² Signup and view all the answers

According to Newton's first law, what happens to a body at rest?

It will remain at rest unless acted upon by an external force. Signup and view all the answers

Which equation represents Newton's second law?

F = ma Signup and view all the answers

How does doubling the distance between two masses affect the gravitational force between them?

It decreases the gravitational force by a factor of 4. Signup and view all the answers

What is impulse in physics?

The change in momentum of an object. Signup and view all the answers

What happens when a football is kicked with more force?

The ball experiences greater acceleration. Signup and view all the answers

What is the SI unit of impulse?

Newton-second (Ns) Signup and view all the answers

How does gravitational force behave according to Newton's law of universal gravitation?

It is directly proportional to the product of their masses. Signup and view all the answers

Which of Newton's laws states that for every action, there is an equal and opposite reaction?

Third law Signup and view all the answers

What will happen to the momentum of an object if its velocity is doubled and its mass remains constant?

It will be doubled. Signup and view all the answers

What force is required to lift a 10 kg object against gravity?

98 N Signup and view all the answers

What phenomenon relates to the conservation of momentum when two bodies collide and stick together?

Completely inelastic collision Signup and view all the answers

What is the relationship between force, mass, and acceleration according to Newton's second law?

Force is the product of mass and acceleration. Signup and view all the answers

What is the unit of measurement for impulse?

Newton-second Signup and view all the answers

Which factor does NOT affect the acceleration due to gravity at different locations on Earth's surface?

Color of the surface Signup and view all the answers

How does momentum behave during a collision between two objects?

Total momentum before collision equals total momentum after Signup and view all the answers

What happens to an object in free fall in a vacuum?

All objects fall at the same rate regardless of mass Signup and view all the answers

What is the significance of calculating the normal reaction force on an inclined surface?

It balances the component of weight perpendicular to the surface Signup and view all the answers

How does friction affect the motion of a car on a level road?

It causes resistance that affects acceleration and deceleration Signup and view all the answers

What does terminal velocity indicate about the forces acting on a falling object?

Weight equals air resistance, resulting in no net force Signup and view all the answers

What occurs to gravitational force when the distance between two masses doubles?

It decreases by a factor of 4 Signup and view all the answers

Which equation represents the calculation of the net force acting on a block being pulled across a surface?

F net = F applied - F friction Signup and view all the answers

What will happen to the momentum of a 70 kg skateboarder moving west at 4 m/s?

It will be 280 kg·m/s west Signup and view all the answers

Why does a spacecraft keep moving to the moon after its engines are turned off?

Inertia keeps it in motion Signup and view all the answers

What do smooth surfaces typically do in terms of friction?

Reduce the frictional force Signup and view all the answers

How can the mass of a system be calculated from the slope of a force vs. acceleration graph?

It equals the reciprocal of the slope Signup and view all the answers

What is the primary reason the value of g varies at different locations on the Earth's surface?

The Earth's mass distribution is uneven. Signup and view all the answers

Which of the following best describes Newton’s law of universal gravitation?

Every point mass attracts every other point mass with a force proportional to the product of their masses. Signup and view all the answers

When a spacecraft's engines are turned off during flight, why does it continue towards the moon?

The initial velocity provides enough momentum to continue without propulsion. Signup and view all the answers

What is a defining characteristic of momentum as a physical quantity?

Momentum depends on the velocity's direction. Signup and view all the answers

What is the SI unit of force and how is it defined?

The SI unit of force is the newton, defined as the force needed to accelerate a 1 kg mass by 1 m/s². Signup and view all the answers

In an experiment to determine the acceleration due to gravity, what is typically the method used to measure time?

Using a stopwatch or digital timer. Signup and view all the answers

Which statement correctly describes friction in a physics context?

Friction opposes the relative motion between surfaces in contact. Signup and view all the answers

What is the relationship described by Newton's first law of motion?

A body in motion will stay in motion unless acted upon by a net force. Signup and view all the answers

How is impulse defined in relation to momentum?

Impulse is the change in momentum resulting from a force applied over time. Signup and view all the answers

What does the principle of conservation of momentum state?

Total momentum before an interaction equals total momentum after the interaction in an isolated system. Signup and view all the answers

When does gravitational force between two masses increase?

When the distance between them decreases. Signup and view all the answers

How is the loss of kinetic energy during a collision accounted for?

Some kinetic energy is transformed into heat, sound, or deformation. Signup and view all the answers

What happens to the forces acting on a book that decelerates on a horizontal table?

A frictional force opposes the book's motion. Signup and view all the answers

What distance is the acceleration due to gravity observed to be approximately equal to on Earth?

9.81 m/s². Signup and view all the answers

Study Notes

Mass and Momentum

Mass measures the amount of matter in a body, quantified using kilograms (kg), which is an SI unit.
It represents an object's resistance to acceleration (inertia) and interacts with gravitational forces.
Momentum (p) is a vector quantity defined as the product of mass and velocity (p = mass × velocity); its unit is kg·m/s.
Total momentum in a closed system before an interaction is equal to total momentum after.

Calculating Momentum

For a skateboarder with a mass of 70 kg moving at 4 m/s, momentum is calculated as p = 70 kg × 4 m/s = 280 kg·m/s west.
The conservation of momentum applies in all directions without external forces; this principle also applies to spacecraft propulsion and collisions, like in snooker.

Conservation of Momentum

In a head-on collision between two identical hockey pucks, if one puck stops, the other puck's velocity can be determined using conservation principles.
In a collision between a skier (90 kg) at 10 m/s and a snowboarder (60 kg) at -5 m/s, they move together at a combined speed of 4 m/s after colliding.

Force

A force is also a vector quantity, measured in newtons (N), where 1 N = 1 kg·m/s².
Newton's three laws of motion frame force concepts:
- Law 1: Objects stay still or move uniformly if no net force acts on them.
- Law 2: Change in momentum relates to applied force; expressed as F = ma.
- Law 3: For every action, there is an equal and opposite reaction.

Impulse and Gravitational Force

Impulse (I) is the change in momentum, measured in newton-seconds (Ns), and acts in the direction of the applied force.
The gravitational force acts between masses, following Newton's Law of Universal Gravitation, which states gravitational force is proportionate to mass and inversely related to the square distance between their centers.

Weight and Acceleration

Weight is a force representing gravitational pull on mass, measured in newtons; weight (W) = mass (m) × acceleration due to gravity (g).
Acceleration due to gravity on Earth is approximately 9.8 m/s², consistent across objects but varies based on distance from Earth's center.

Friction and Terminal Velocity

Friction opposes motion between two surfaces and increases with velocity; it enables controlled movement or stopping.
At terminal velocity, downward weight equals upward air resistance, leading to constant falling speed.

Experimental Setup and Observations

Experiments illustrate conservation of momentum, using trolleys or pendulums, measuring pre and post-collision velocities.
Precautions in experiments include minimizing friction and using consistent masses.

Common problems involve calculating net force, acceleration, and momentum through various scenarios, often applying F = ma and concepts of impulse and momentum conservation.
Real-life examples include a golfer's trolley dynamics and projectile motion of a golf ball, needing to consider angles and forces during calculations.

Understanding Gravity Variations

Gravity varies across Earth's surface due to shape and mass distribution; potential exam questions will address effects of altitude and location on gravitational acceleration.### Physics Concepts and Principles
Forces on a Skydiver:
- Gravitational force acts downward (weight).
- Air resistance acts upward (drag).
- At constant velocity, gravitational force equals air resistance, resulting in zero net force.
Newton's Law of Universal Gravitation:
- States that every point mass attracts every other point mass with a force proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
- Formula: ( F = G \frac{{m_1 m_2}}{{r^2}} )
Acceleration due to Gravity at Height:
- At a height equal to twice the radius of Earth, gravitational acceleration can be calculated using ( g' = g \frac{{R^2}}{{(R+h)^2}} ), with ( h = R ).
- Results in ( g' = \frac{g}{4} ) (where ( g = 9.81 , \text{m/s}^2 )).
Spacecraft Motion:
- Spacecraft continues to the moon due to inertia, as per Newton's First Law, which states an object in motion stays in motion unless acted upon by an external force.
Lack of Atmosphere on the Moon:
- The moon's low gravity (approximately 1/6th of Earth) cannot hold an atmosphere securely.
- Solar wind and lack of magnetic field contribute to the absence of an atmosphere.

Friction and Motion

Definition of Friction:
- Friction is the force opposing relative motion between two surfaces in contact.
Factors Affecting Friction:
- Increases with the weight of the object.
- Varies based on the texture and materials of the surfaces.
Force on a Car:
- Engine force: 2.0 kN leading to acceleration of 1.2 m/s².
- Net force calculated from Newton's second law.
- Friction counteracts motion and cannot exceed the engine's force.

Experiments in Physics

Measuring Acceleration:
- Acceleration can be measured by plotting a graph of force against acceleration.
- The slope of the line can be used to find mass.
Conservation of Momentum:
- Total momentum before a collision equals total momentum after in a closed system.
- Example: A collision between two bodies shows momentum conservation by equating the mass and velocity before and after.
Gravity Experiments:
- Use a ball to measure the time it takes to fall through a certain distance.
- The slope of a distance vs. time squared graph gives the value of gravitational acceleration.

Key Formulas and Definitions

Momentum:
- Definition: Momentum (p) is given by ( p = \text{mass} \times \text{velocity} ).
Newton's Laws:
- First Law: An object remains at rest or in uniform motion unless acted upon by a net force.
- Second Law: The acceleration of an object is proportional to the net force acting on it and inversely proportional to its mass (( F = ma )).
Defining Units:
- SI unit of mass is the kilogram (kg).
- One Newton is defined as the force needed to accelerate a mass of 1 kg by 1 m/s².

Impact of Variables on Physics Principles

Changes in Momentum:
- Momentum conservation applies in collisions; total before equals total after.
- The direction affects calculations as momentum is a vector quantity.
Atmospheric Effects:
- Weightlessness occurs in a vacuum as there are no air resistance effects.
- Varying gravitational acceleration on Earth's surface due to mass distribution and altitude changes.
Experimental Errors:
- Graphs not passing through the origin indicate systematic errors or external forces not accounted for.
- Using dense objects minimizes air resistance for accurate free-fall measurements.

Important Relationships

Acceleration due to Gravity:
- Lower at greater distances from Earth's center; factors include altitude and Earth's non-uniform shape.
Friction's Role:
- Essential for traction but acts against motion, influencing speed and acceleration outcomes on surfaces.

Each topic presents essential physics concepts and their practical implications, useful for studying the principles underlying motion, force, and gravitational effects.

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Description

This quiz covers the concepts of mass and momentum in physics. Learn about how mass measures matter and its role in inertia and gravitational interactions, as well as the calculation of momentum as a vector quantity. Test your understanding of these fundamental principles in mechanics.