The Sky’s the Limit

Terms Acceleration Aerodynamics Air Pressure Balanced forces Drag Force Gravity Lift Mass Propulsion Thrust Unbalanced forces

Acceleration The rate of change of an object’s speed with time. To speed up, an object must accelerate; to slow down, it decelerates.

Aerodynamics The science that deals with the flow of air around an object in motion.

Air pressure The amount of force air exerts on an object.

Balanced Forces Forces that do not produce motion when they interact.

Drag The aerodynamic force that acts against an object moving through air or another fluid.

Force A push or pull that makes an object move, or change speed or direction if it is already moving.

Gravity The force that attracts things toward the centre of large objects. Earth's gravity causes people and objects to have weight.

Lift The aerodynamic force that acts perpendicular to the direction of motion, causing an object to rise.

Mass The amount of matter in an object.

Propulsion A driving force that pushes an object.

Thrust The force that pushes a flying object forward. An aircraft engine produces thrust that propels the craft.

Unbalanced forces Forces applied at the same time that produce acceleration when they interact.

Explain how a hot air balloon works. The air in a hot air balloon is heated by a propane burner at the base of the balloon. Once the air inside the balloon has been heated the balloon will rise because the hot air is lighter than the cold air surrounding the balloon. The balloons weight is controlled by turning the burner on and off when needed allowing the balloon to rise and land.

The movement of a shower curtain after a shower is turned on show Bernoulli’s principle. Describe how it represents Bernoulli’s Principle.

Bernoulli’s Principle Fast moving water gushes past the shower curtain. As Bernoulli’s principle states, this fast moving water will cause low pressure on the inside part of the shower curtain. Therefore, on the other side of the curtain is high pressure. This high pressure pushes against the low pressure and causes the shower curtain to move inwards.

Explain kayakers use resistance. Isaac Newton put forward a law of motion. It states that every action has an equal and opposite reaction. As a kayak moves through water, it pushes the water and the water pushes back. If the rudder is turned slightly on way or the other, the sideways angle of resistance turns the boat. The boat must be moving for the rudder to work – if not there is no speed, no resistance and no force.

Name 4 facts about lift Lift depends on shape – lift is greater with an airfoil-shaped wing than with a flat one. Lift depends on angle of attack – up to a point, lift increases as the angle of attack increases. Lift depends on speed – lift increases as speed increases. Lift depends on direction – lift acts perpendicular to the direction of the objects movement.

Why are the wings of a plane curved? When an airplane moves forward, air moves backward over and under its wing. The air moving above the wing moves more quickly because of the curved top. As the higher pressure air beneath the aircraft tries to move up to the area of lower pressure, it presses up on the plane. When the lift becomes greater than the force of gravity, the airplane rises into the air.