P5 - Space For Radiation Flashcards
What is the mathematical relationship between gravitational force and the distance between two objects?
Gravity is inversely proportional to the square of the distance (inverse square law).
In other words, when you double the distance, the gravitional force decreases by a factor of 4 (2 squared).
Or, when you halve the distance, the gravitional force increases by a factor of 4.
When a comet orbits around the sun, why does its speed change throughout its journey?
- Comets orbit the sun is an elliptical (oval-shaped) path.
- The sun isn’t at the centre of this orbit, but skewed toward one side.
- This means, at the parts of its orbit where it is nearer the sun, the gravitational force is greater. Therefore, in these parts it will also travel much faster.
- On the other hand, when it is further away from the sun, it will have less gravitational attraction and will therefore travel slower.
Why does a planet further away from the sun take longer to complete one orbit (an orbital period)?
- It is further away from the sun, therefore the circumference of its orbit will be greater.
- Furthermore, it will travel slower because it is further away from the sun as the force of gravity will be weaker.
Describe the orbit of a geostationary satellite.
- Remains in fixed position above the Earth’s surface.
- Orbits around the Earth once every 24 hours.
- Orbits around the equator line.
Why do artificial satellites need a tangential motion?
- Due to the gravitational force of attraction, satellites are constantly accelerating toward the Earth.
- However, their forward speed (also called tangential motion) is what ensures the satellites travel in a circular orbit.
- This is because the resultant vectors of the acceleration toward Earth (gravity) and the tangential motion produce a circular orbit.
What does all circular motion require?
A centripetal force.
In the case of orbits, that force is gravity.
Why do artificial satellites in lower orbits travel faster than those in higher orbits?
The force of gravity is much greater when the distance between the satellite and Earth is shorter. Therefore, the speed of lower orbit satellites will be much faster than higher orbit ones.
Why do weather and spying satellites need to be in lower orbit?
- When they’re too high, the resolution of the weather or spy images will be too low.
- They travel really quickly, meaning that all parts of the Earth can be monitored each day (they have a much lower orbital period).
Why do weather and spying satellites need to be in polar orbits?
In a polar orbit, the satellites will sweep over both poles while the Earth rotates underneath. This means that all areas of the Earth can be monitored over a small period of time.
In the equations of motion, what do the 5 variables represent (s,u,v,a,t)
s = distance (m) u = initial velocity (m/s) v = final felocity (m/s) a = acceleration (m/s2) t = time (seconds)
What is the optimum angle to launch a ball to achieve the greatest range?
45 degrees
What is the resultant velocity of any projectile?
The vector sum of its horizontal and vertical velocity.
Why does a ball, when kicked from the ground at 45 degrees, travel in a parabolic motion?
- It’s horizontal velocity stays constant as there are no forces (ignoring air resistance) acting on the projectile in the horizontal direction.
- However, the force of gravity means that the projectile is acceleration downward in the vertical direction.
- The vector sums of this projectile’s horizontal motion and increasing vertical motion form a curved path.
What is Newton’s third law of motion?
When any object collides with another object, the two objects exert equal and opposite forces on eachother.
When a book with a weight of 10N is put on a table, what is the upward reaction force being applied to the book by the table?
10N
Because of Newton’s third law of motion.
In terms of Newton’s third law: When a bullet is fired from the gun, why does the gun recoil in the opposite direction to the bullet?
- When the gun is fired, the gun exerts a force on the bullet that means it is fired outward.
- Due to the Newton’s third law, the bullet also exerts an equal but opposite reaction force onto the gun itself.
- Therefore, the gun experiences recoil as it travels backward.
What is meant by the conservation of momentum?
When two objects collide, the total momentum before the collision is the same as the total momentum after the collision.
How does the conservation of momentum explain rocket propulsion?
- Rocket releases exhaust gases backwards.
2. The rocket moves forward because the momentum is conserved.
How does the conservation of momentum explain explosions?
- Before an explosion, total momentum is zero.
- When an object explodes, particles are thrown out in all directions and speeds.
- When all of these different momentums are added together, they add up to zero (hence why explosions happen in all directions).
Why, in terms of the particle model, does reducing the volume of the container increase the pressure?
If you decrease the volume of the container, the particles will be more squashed. Therefore, they will collide with the walls more often - increasing the pressure.
