Physics

Moment (Nm) = Force (N) X Distance (metres,m)

Centre Of Mass is the point on an object where all the mass is concentrated

Principle Of Moments:sum of all clockwise moments=sum of all anti-clockwise moments

Factors of stability are the width of base and the height of the centre of mass

Factors of Centripetal force:

• increases if speed increases
• increases if radius of circle decreases
• increases if mass of object increases

Newton's Rules of Gravity:

• is an attractive force
• increases as mass of each object increases
• decreases if distance between two objects increases

Gravitational Field Strenght of Earth is 10N/Kg

To stay in orbit at a particular distance, a planet must move at a particular speed around the Sun.

The further a planet is from the Sun, the less its speed is.

The further a planet is from the Sun, the longer it takes to make a complete orbit.

The period of a sattelite is the time taken for one complete orbit.

Geostationary Satellites:

• Orbit above the equator
• Have a period of 24 hours
• Orbit in same direction as Earth's spin
• Stay above the same place
• Are used for communcations

Monitoring Satellite:

• Are fitted with TV cameras
• Are in lower orbits than geostationary satellites
• To see Earth in greater detail
• Period of 2-3 hours
• Orbit over the poles
• Scan the whole Earth every day
• Used for weather forecasting, military and police surveillance and environmental monitoring.

Convex mirror, bends in.

Concave mirror, bends out.

Image in mirror is due to reflection of light.

Angle of incidence=Angle of reflection

Image in mirror is virtual

Image on screen is real.

Distance from mirror to principal focus= focal lenght

Magnification is image height/object height.

For concave mirror:

•Light ray parallel to axis and reflected through focal point •Light ray through centre and reflected at equal angle

•Light ray through focal point and parallel to axis Light changes direction through lenses, known as refraction. Light bends towards normal when entering and away from normal when exiting.