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?

The rate of change of speed. Signup and view all the answers

What indicates negative acceleration?

A decrease in speed. Signup and view all the answers

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

Length of card divided by time beam is blocked. Signup and view all the answers

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

Force equals mass multiplied by acceleration. Signup and view all the answers

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

It will accelerate in the direction of the net force. Signup and view all the answers

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

2 m/s² Signup and view all the answers

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

490 N 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?

Acceleration will decrease by half. Signup and view all the answers

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

9.8 N/kg Signup and view all the answers

Which of the following statements about weight is true?

Weight varies with the gravitational field strength. 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?

140 N Signup and view all the answers

What is the unit of measurement for acceleration?

Metres per second per second Signup and view all the answers

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

The distance traveled by the object Signup and view all the answers

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

Double card and two light gates Signup and view all the answers

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

Constant speed Signup and view all the answers

When is acceleration considered negative?

When the object slows down Signup and view all the answers

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

By finding the area under the graph Signup and view all the answers

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

Acceleration increases Signup and view all the answers

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

11.3 N/kg Signup and view all the answers

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

It is heavier on Jupiter. Signup and view all the answers

Which benefit of space exploration involves improving communication systems?

Communication Signup and view all the answers

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

Non-stick frying pans Signup and view all the answers

Which planet has the weakest gravitational field strength?

Moon Signup and view all the answers

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

9.8 N Signup and view all the answers

In what way has space exploration contributed to mapping technologies?

Through satellite mapping of Earth Signup and view all the answers

Which aspect of space exploration has aided in weather prediction?

Satellite imaging Signup and view all the answers

What is a major risk associated with space debris?

Debris poses a risk of falling to Earth. Signup and view all the answers

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

It may bounce back into space. Signup and view all the answers

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

Heat resistant tiles Signup and view all the answers

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

Ablation Signup and view all the answers

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

Kinetic energy is converted into heat energy. Signup and view all the answers

What distinguishes geostationary satellites from lower orbiting satellites?

They orbit at a higher altitude and take 24 hours to complete an orbit. Signup and view all the answers

What is a function of orbiting satellites?

They can be used for weather observation. Signup and view all the answers

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

The heat absorbed to melt the heat shield material. Signup and view all the answers

What is the primary function of satellites?

Telecommunications and weather observation Signup and view all the answers

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

Curved dish transmitters Signup and view all the answers

How is distance measured in space?

In light years Signup and view all the answers

What defines an exoplanet?

A planet outside our Solar System Signup and view all the answers

What is the approximate distance light travels in one year?

9.5 million million kilometers Signup and view all the answers

What constitutes our Solar System?

A single star and its planets Signup and view all the answers

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

It is only composed of planets Signup and view all the answers

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

At least 100 billion Signup and view all the answers

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.