Physics Class: Motion and Forces
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Questions and Answers

How is average speed calculated?

  • Distance travelled divided by time taken. (correct)
  • Speed multiplied by time.
  • Distance squared divided by time.
  • Time taken divided by distance travelled.

What does an instantaneous speed measure?

  • Speed based on fuel consumption.
  • The maximum speed a vehicle can reach.
  • Speed measured over very short distances or time intervals. (correct)
  • Speed averaged over a long distance.

Which device is used to measure instantaneous speed?

  • Light gate with a timing device. (correct)
  • Odometer.
  • Speedometer only.
  • GPS devices.

What aspect of motion does acceleration describe?

<p>The rate of change of speed. (D)</p> Signup and view all the answers

What indicates negative acceleration?

<p>A decrease in speed. (B)</p> Signup and view all the answers

Which of the following correctly defines the formula for instantaneous speed?

<p>Length of card divided by time beam is blocked. (D)</p> Signup and view all the answers

What is the relationship between force, mass, and acceleration?

<p>Force equals mass multiplied by acceleration. (A)</p> Signup and view all the answers

If an object is acted upon by a net unbalanced force, what happens to the object?

<p>It will accelerate in the direction of the net force. (A)</p> Signup and view all the answers

Calculate the acceleration of a 70 kg object subjected to a net force of 140 N.

<p>2 m/s² (A)</p> Signup and view all the answers

What is the weight of a mass of 50 kg under Earth's gravitational field strength?

<p>490 N (A)</p> Signup and view all the answers

If the mass of an object is doubled, how does that affect the acceleration if the force remains the same?

<p>Acceleration will decrease by half. (D)</p> Signup and view all the answers

What is the gravitational field strength near the Earth's surface?

<p>9.8 N/kg (D)</p> Signup and view all the answers

Which of the following statements about weight is true?

<p>Weight varies with the gravitational field strength. (A)</p> Signup and view all the answers

If two forces of 200 N and 60 N act on a cyclist in opposite directions, what is the resultant force?

<p>140 N (C)</p> Signup and view all the answers

What is the unit of measurement for acceleration?

<p>Metres per second per second (C)</p> Signup and view all the answers

What information can be obtained from a speed-time graph regarding the motion of an object?

<p>The distance traveled by the object (A)</p> Signup and view all the answers

Which of the following is used to measure acceleration using light gates?

<p>Double card and two light gates (D)</p> Signup and view all the answers

What does a horizontal line on a speed-time graph represent?

<p>Constant speed (C)</p> Signup and view all the answers

When is acceleration considered negative?

<p>When the object slows down (B)</p> Signup and view all the answers

How can the distance traveled by an object be calculated from its speed-time graph?

<p>By finding the area under the graph (A)</p> Signup and view all the answers

What happens to the acceleration if the speed of an object changes rapidly in a short time?

<p>Acceleration increases (C)</p> Signup and view all the answers

What is the value of the gravitational field strength on Neptune?

<p>11.3 N/kg (B)</p> Signup and view all the answers

How would the weight of an object with a mass of 10 kg compare on Jupiter versus Earth?

<p>It is heavier on Jupiter. (D)</p> Signup and view all the answers

Which benefit of space exploration involves improving communication systems?

<p>Communication (B)</p> Signup and view all the answers

What is one example of spin-off technology from the space industry?

<p>Non-stick frying pans (D)</p> Signup and view all the answers

Which planet has the weakest gravitational field strength?

<p>Moon (C)</p> Signup and view all the answers

What is the weight of a 1.2 kg hammer on Earth?

<p>9.8 N (A)</p> Signup and view all the answers

In what way has space exploration contributed to mapping technologies?

<p>Through satellite mapping of Earth (A)</p> Signup and view all the answers

Which aspect of space exploration has aided in weather prediction?

<p>Satellite imaging (A)</p> Signup and view all the answers

What is a major risk associated with space debris?

<p>Debris poses a risk of falling to Earth. (C)</p> Signup and view all the answers

What happens to a spacecraft when it re-enters the Earth's atmosphere at a wrong angle?

<p>It may bounce back into space. (D)</p> Signup and view all the answers

Which material is used to protect the space shuttle during re-entry?

<p>Heat resistant tiles (A)</p> Signup and view all the answers

What process does the heat shield undergo to protect the spacecraft during re-entry?

<p>Ablation (C)</p> Signup and view all the answers

How does energy transform during the re-entry of a spacecraft?

<p>Kinetic energy is converted into heat energy. (A)</p> Signup and view all the answers

What distinguishes geostationary satellites from lower orbiting satellites?

<p>They orbit at a higher altitude and take 24 hours to complete an orbit. (A)</p> Signup and view all the answers

What is a function of orbiting satellites?

<p>They can be used for weather observation. (B)</p> Signup and view all the answers

What is the latent heat of fusion related to during spacecraft re-entry?

<p>The heat absorbed to melt the heat shield material. (D)</p> Signup and view all the answers

What is the primary function of satellites?

<p>Telecommunications and weather observation (C)</p> Signup and view all the answers

What is a key component of a satellite's communication system?

<p>Curved dish transmitters (B)</p> Signup and view all the answers

How is distance measured in space?

<p>In light years (D)</p> Signup and view all the answers

What defines an exoplanet?

<p>A planet outside our Solar System (B)</p> Signup and view all the answers

What is the approximate distance light travels in one year?

<p>9.5 million million kilometers (D)</p> Signup and view all the answers

What constitutes our Solar System?

<p>A single star and its planets (D)</p> Signup and view all the answers

Which of the following is not a characteristic of a galaxy?

<p>It is only composed of planets (A)</p> Signup and view all the answers

What is the estimated number of planets in the Milky Way?

<p>At least 100 billion (B)</p> Signup and view all the answers

Flashcards

Instantaneous Speed

The speed of an object at a specific moment in time. It is the speed measured over a very short distance or time interval.

Average Speed

The average speed of an object over a longer period of time or distance. It is calculated by dividing the total distance travelled by the total time taken.

How to calculate speed

Distance travelled divided by the time taken.

Acceleration

The rate at which an object's speed changes. It can be positive (speeding up) or negative (slowing down).

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Light Gate

A device used to measure an object's speed over a short distance. It consists of a light source, photocell, and a timer.

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Card (in a Light Gate)

An object that blocks the beam of light in a light gate, allowing the measurement of its length and time it takes to pass through.

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Distance

The distance covered by an object in a specific period of time.

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Time

The duration it takes for an object to cover a certain distance.

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Newton's Second Law of Motion

The net force acting on an object is directly proportional to the object's acceleration and inversely proportional to its mass.

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Unbalanced Force

The force that results from an unbalanced force on an object. It is the force that causes the object to accelerate.

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Gravity

The force that attracts objects towards each other due to their masses.

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Gravitational Field Strength

The strength of a gravitational field at a specific point, measured in newtons per kilogram (N/kg).

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Mass

The amount of matter in an object, measured in kilograms (kg).

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Weight

The force with which gravity pulls on an object's mass, measured in newtons (N).

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F = m x a

The equation that relates force, mass, and acceleration: Force = Mass x Acceleration.

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What is acceleration?

The rate at which an object's speed changes.

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How to calculate acceleration?

The formula for calculating acceleration is: a = ∆v / t, where 'a' is acceleration, '∆v' is the change in speed, and 't' is the time taken for the change.

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What are the units of acceleration?

Units for measuring acceleration are meters per second per second (m/s²).

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What is a speed-time graph?

A speed-time graph illustrates the relationship between an object's speed and time. The shape of the graph provides information about the object's motion.

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How do you interpret a speed-time graph?

A horizontal line on a speed-time graph represents an object at rest, while an inclined line indicates constant speed.

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What does the area under a speed-time graph represent?

The area under a speed-time graph represents the distance travelled by the object.

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What are light gates?

Light gates are devices used to measure the speed of an object over a short distance. They consist of a light source, photocell, and a timer.

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How can light gates be used to measure acceleration?

Light gates can be used to measure acceleration by determining both the initial and final speeds of an object. This can be achieved using a double card or a single card and two light gates.

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Gravitational Field Strength (g)

The strength of a gravitational field at a specific location. Measured in newtons per kilogram (N/kg).

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Satellites

Artificial satellites orbiting Earth, used for communication, navigation, and weather monitoring.

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Spin-off Technologies

Technologies initially developed for space exploration, later adapted for everyday use.

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Space Exploration

The exploration of space and the technology involved.

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Benefits of Space Exploration

Benefits of space exploration include advancements in communication, navigation, weather monitoring, and job creation.

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Risks of Space Exploration

The potential risks of space exploration, such as financial cost, environmental impact, and safety concerns.

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What is a planet?

A body that orbits a star.

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What is a moon?

A body that orbits a planet.

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What is a star?

A giant ball of burning gas found at the center of a solar system.

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What is a solar system?

A star and all the planets that orbit it.

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What is a galaxy?

A collection of many solar systems.

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What is a light year?

The distance that light travels in one year.

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What is an exoplanet?

A planet that orbits a star outside of our solar system.

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How do satellite receivers work?

A way for satellites to receive and send signals using a curved dish to focus the signal onto an antenna.

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Re-entry Heat

When a spacecraft re-enters Earth's atmosphere at high speed, it experiences friction due to the air, generating significant heat.

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Heat Resistant Tiles

The space shuttle was covered in heat-resistant tiles to withstand the extreme temperatures during re-entry.

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Ablation

Older spacecraft used a technique called ablation where a heat shield melted to absorb excess heat, preventing damage to the spacecraft.

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Latent Heat of Fusion

The heat absorbed by the heat shield as it melts is known as the latent heat of fusion.

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Orbiting Satellites

Satellites orbiting close to Earth are used for various purposes like mapping, weather monitoring, and military applications.

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Geostationary Satellites

Geostationary satellites maintain a fixed position relative to Earth, orbiting at a higher altitude and completing one revolution every 24 hours.

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Space Debris Risk

The risk of debris from satellites or spacecraft falling back to Earth and posing a threat to the surface exists, although the likelihood is extremely low.

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Danger to Life in Space

Astronauts face dangers during space missions, including potential loss of life, which emphasizes the risks involved in space exploration.

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Study Notes

Speed and Acceleration

  • Speed is calculated by dividing the distance traveled by the time taken. Average speed is measured over long distances or time intervals.
  • Average speed = distance traveled / time taken (v = d/t)
    • v = final speed (m/s)
    • d = distance (m)
    • t = time (s)
  • Instantaneous speed is measured over very short distances or time intervals, like a car's speedometer.
  • Electronic methods, using light gates and computers, can measure instantaneous speed.

Acceleration

  • Acceleration is the rate of change in speed. Positive acceleration is speeding up, and negative acceleration is slowing down.
  • Acceleration = change in speed / time taken (a = Δv/t)
    • a = acceleration (m/s²)
    • Δv = change in speed (m/s)
    • t = time (s)
  • Light gates can be used to measure acceleration by measuring initial and final speeds. A double card or two light gates are used.

Speed-Time Graphs

  • Speed-time graphs show an object's motion. Shape of the graph indicates different types of motion.
  • At rest: horizontal line
  • Constant speed: horizontal line
  • Acceleration or speeding up: upward sloping line
  • Negative acceleration or slowing down: downward sloping line
  • Area under a speed-time graph = distance traveled.

Measuring Acceleration from Speed-Time Graphs

  • Acceleration can be found by calculating the slope of a speed-time graph.
  • Acceleration = change in speed / time taken (a = Δv / t)

Forces, Motion, and Energy

  • Force is measured in newtons (N).
  • Force changes the shape, speed, and direction of an object.
  • Balanced forces: No change in motion.
  • Unbalanced forces: Acceleration occurs.
  • Resultant force: Net force acting on an object
  • Equation: Force = mass × acceleration (F = m × a)

Newton's First Law of Motion

  • An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Newton's Second Law of Motion

  • The acceleration of an object is directly proportional to the net force acting on the object, and inversely proportional to the object's mass (F = ma).

Weight and Gravity

  • Weight is the force of gravity on an object. It's measured in newtons (N).
  • Weight = mass × gravitational field strength (W = m × g).
  • Gravitational field strength varies on different celestial bodies.

Frictional Forces

  • Friction opposes motion.
  • Useful friction: prevents slipping, helps braking
  • Unhelpful friction: increases noise, reduces efficiency

Space Exploration

  • Benefits include communication, navigation, job creation, mapping, and weather monitoring.
  • Risks include space debris, danger to life, high costs.

Re-entry and Heat

  • Friction with the atmosphere creates intense heat during re-entry.
  • Heat shields (ablation) prevent damage.

Satellites

  • Orbiting satellites: used for mapping, weather, military purposes.
  • Geostationary satellites: used for telecommunications/weather observation.

Cosmology

  • Planets orbit stars
  • Stars are balls of burning gas
  • Solar system is a star and its associated planets
  • Galaxy groups solar systems
  • Universe is all known matter
  • Light-year: Distance light travels in a year (9.5 million million kilometers approximately)
  • Exoplanets: planets outside our solar system

Life on Other Planets

  • Factors for life: orbit, distance from star, size, gravitational field strength, presence of water, atmosphere.

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Description

Test your understanding of key concepts in physics related to motion and forces. This quiz covers average speed, instantaneous speed, acceleration, and the relationships defined by Newton's laws. Prepare to challenge your knowledge with practical examples and calculations.

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