# P5a

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1. What is a satallite?
An object that orbits a planet in space. They can be natural or artificial.
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2. How is a satallie kept in orbit?
A gravitational force. Gravity is a universal force of attraction between masses.
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3. What is a centripal force?
Acts towards the centre of a circle. It keeps an object moving in a circle. Gravity provides the centripal force that keeps a satallite in orbit.
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4. What is the equation for the weight on an object?
Weight = mass x gravitational field strength.
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5. What is the inverse square law?
The gravitational force between two objects gets weaker as the objects are moved further apart. If the distance is doubled, the force drops to 1/4.
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6. The difference in gravitational force means that....
Planets closer to the sun travel quickly and have short orbital periods. Planets further away from the sun travel slowly and have long orbital periods.
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7. How do periodic comets orbit?
Almost eliptical loops, unlike planets, which have almost-circular orbits.
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8. What happens to a comet if it is near the sun or further away from the sun?
When a comet is near the sun it has to travel quickly to escape the gravitational force. When the comet is further away, it travels more slowly because the suns gravity is pulling it back.
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9. How is this effect similar to ones of a football.
As you throw a ball up in the air it slows down and as it gets closer to earth it speeds up.
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10. When does a satallites orbital period increase?
With height above the earth.
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11. What does the height of a satallite determine?
What it can be used for.
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12. Explain satallites in low orbit and their uses.
Travel very quickly, go around the earth several times a day. Their uses are imaging earths surface, weather forcasting, military uses.
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13. What are satallites in high orbit called and explain them and their uses.
Geostationary satellites - orbit much higher than earth, take 24 hours to complete circuit, remain in a fixed position above earths surface. Communitcation, satellite television and weather forcasting.
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14. What causes satellites to contiually accelerate towards earth and the satellites going off on a tangent?
Gravity
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15. What would satellites naturally do if there was no gravity?
They would travel in a straight line.
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16. Why does the satellite remain in a circular orbit?
Because the speed of the satellite and gravity balance.
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17. What is a scalar quantity?
A size only.
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18. Give an example of a scalar quantity.
Mass, energy, speed and time.
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19. What is a vector quantity?
A size and a direction.
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20. Give examples of vector quantities.
Velocity, Force and acceleration.
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21. What is speed?
How fast something is moving at a particular time. Or how much distance it covers over a period of time.
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22. Is speed a scalar or vector quantity?
Scalar.
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23. What is the equation for average speed?
Distance/Time.
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24. What is a relative speed?
It is described as relative speed if two objects are moving near each other, and their motion is described.
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25. What is the relative speed of a car travelling towards each other on a straight road. Each car travelling at 10m/s.
20m/s. If you are in either car then it will seem like the car is travelling at you at 20 m/s.
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26. What is the relative speed of two cars travelling in the same direction. Car D is travelling at 8m/s and car C is travelling at 10m/s.
2m/s. Every second car C is getting 2m closer to car D.
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27. What is velocity?
An objects rate of displacement, (change in distance).
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28. What are the equations 4 equations of motion?
v = u + at s = ((u+v)/2) x t v2 = u2 +2as s = ut +0.5at2
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29. When is it possible to create a vector diagram?
When the two forces are parallel and you want to calculate their total effect.
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30. What do parallel vectors in the same direction do?
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31. What do parallel vectors in different directions do?
Subtract
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32. What can you do if two forces are acting at right angles?
You can work out the resultant force/velocity by using pythagoras' theorem.
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33. What are objects called if they are fired into the air?
Projectiles.
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34. Give some examples of projectiles.
Gold balls, footballs, darts, long jumpers, netballs, bullets etc
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35. What is the path that the projectile takes called?
Trajectory.
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If a projectile is launched in the air and has no air resistance acting upon it, the projectile will have.....?
A constant horizontal velocity and a steadily increasing vertical velocity.
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37. If air resistance is ignored, what is the only force acting upon projectiles?
Gravity
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38. What are horizontal and vertical velocities examples of?
Vectors.
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39. What velocity does the earth's gravity effect?
Vertical velocity.
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40. What is the name for objects projected horizontally on Earth following a downward path?
Parabolic trajectory.
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41. What does the horizontal range depend on?
The launch angle, measured from horizontal.
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42. Footballs launched at 45 degrees will.......
travel the greatest distance.
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43. How is the resultant velocity calculated?
The vector sum of the horizontal and vertical velocities.
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44. A projectile has ............. acceleration in the horizontal direction. Because.............................................
No - gravity only affects its vertical velocity.
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45. Every action has a .......................
equal and opposite reaction.
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46. What happens when an object collides with another?
They excert equal and opposite forces on each other. This is Newtons Third Law of Motion.
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47. Give an example of the Third Law of motion when you stand on the ground.
You excert a force on the ground (your weight) and the ground exerts an equal and opposite force on you (contact force).
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48. How do you calculate momentum?
Momentum = mass x velocity.
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49. In a collision, the velocities of the objects colliding are?
Parallel.
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50. What is acceleration?
The rate of change of an object's velocity over time.
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51. What are many injuries in vehicle collisions and sporting collisions caused by?
Rapid accelerations (using a sudden slowing down) of the body.
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52. What do safety features in a car do?
They reduce injury by spreading out the acceleration over a greater period of time. This means that the passengers momentum is reduced more slowly.
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53. What is the equation for force?
Force (N) = Change in momentum/Time.
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54. Is the total amount of momentum the same or different to the momentum there was before?
The same.
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55. Explain the conservation of momentum in recoil.
Total momentum of gun and bullet is zero. When the bullet is fired the total momentum is still zero. The bullet moves faster than the gun but has a smaller mass, so their momentum is in opposite directions, cancelling each other out.
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56. Explain the conservation of momentum in an explosion.
Before and explosion, the total momentum is zero. After an explosion each fragement flies off in a different direction. The momentum of one fragment will cancel out the momentum of another fragment travelling in the opposite direction, same momentum.
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57. Explain the conservation of momentum in a rocket propulsion.
When a rocket's engine fire into space, the rocket speeds up, but the total momentum of the system is conserved. This is because the forward momentum of the rocket is cancelled out by the backward momentum of the gas it fires out.
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58. Explain the conservation of momentum in a collision.
During a collision, momentum is conserved. If two objecst join during the collision, the momentum after the collision must equal the sum of their two individual momentums.
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59. What is the equation for the conservation of momentum?
m1u1 +m2u2 = (m1 + m2) v
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60. Gas particles are in constant motion. So as particles collide with walls of their container they?
excert a force on the wall.
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61. What is force per unit called?
Pressure.
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62. The greater the number of collisions between the particles and the wall, the .............. the pressure inside the container.
greater
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63.What happens if the gas particles are squashed into a smaller volume?
The same number of particles will have less space. Each particle will collide with the walls more frequently. The pressure increases.
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64. What happens if the temperature of the gas increases?
The particles gain energy. Increased kinetic energy, particles move more quickly. Each particle will collide with the wall more frequently and with more force. Pressure increases.
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65. What happens as a particle strikes a wall of the container?
It undergoes a change in momentum.
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66. What is required to launch a rocket?
A large force provided by the exhaust gases.
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67. What equals the forward force of the gas on the rocket?
The force pushing backwards out of the rocket.
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68. What produces a force on the rocket?
The fast-moving particles in the gas collide with the walls of the rocket.
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69. What allows the rocket and satallite to be launched into space?
A large number of particles of exhaust gas and the particles moving at high speed.
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## Other cards in this set

### Card 2

#### Front

2. How is a satallie kept in orbit?

#### Back

A gravitational force. Gravity is a universal force of attraction between masses.

### Card 3

#### Front

3. What is a centripal force?

### Card 4

#### Front

4. What is the equation for the weight on an object?

### Card 5

#### Front

5. What is the inverse square law?