Science forces ( 9.2) Flashcards
(24 cards)
What are contact forces?
Forces acting between 2 objects that are in physical contact with each other are called contact forces.
What is friction?
Friction is the force that opposes motion between two surfaces in contact.
How does Friction help us?
Friction allows us to hold on to things without dropping them. We are also able to walk without slipping often due to friction.
What is Elastic force?
Elastic force is the force thatching on a stretched or compressed elastic object to return to its original state.
Why do climbers use chalk?
Chalk helps to absorb moisture on the climber’s hands, which increases friction and improves their grip on the rock wall.
What are non-contact forces?
Non-contact forces are forces that act between two objects that are not touching each other.
How do Maglev trains move so fast?
As the Maglev train moves on the track, the angelic force of repulsion lifts it slightly as one the track. This greatly reduces friction between the train and the track, allowing the train to travel at a higher speed.
What is weight?
Weight is the measure of the gravitational force acting on a object.
What is mass?
Mass is the amount of matter in an object
State the SI unit of mass and weight respectively.
Mass: Kilogram ( kg)
Weight: newton (N)
How do you measure forces with a spring balance?
The spring in a spring balance stretches when a force pulls on it. The weight of an object can then be read directly offf the scale on the spring balance.
How do you measure mass?
Use a beam balance or an electronic balance.
How can force affect things?
( Turning effect)
A force applied on an object can cause a turning effect about a fixed point called the pivot.
How can force affect things?
(Size/Shape)
When a force exerted causes the transfer of energy between objects, the size/shape may change.
What is Pressure?
Pressure is the amount of force applied per unit area.
Pressure formula
P = F-N/A-m
SI unit for pressure
Newton per square meter( N/m2) or Pascal (Pa)
Why are needles used from injections sharp?
An injection needle needs to be very sharp so that the area of contact of the needle with the skin is very small. Hence there is higher pressure exerted onto the skin, which allows the sharp needle to pierce the skin easily.
Why is a sharper knife better to cut tomatoes?
A sharp knife has a smaller area of contact with a tomato than a blunt knife. With the same amount of force applied, a sharp knife exerts a higher pressure than a blunt knife. Thus it is able to cut tomatoes more easily.
Why does base of a dam have a thicker wall than than its top?
Water pressure is higher at the base of a dam. Hence a thicker wall there is able to withstand the higher pressure.
What should be done to dams when seal levels rise due to climate change?
The base of the dam will need to have a thicker wall as the water pressure at the seabed increases with more water. Hence the thicker wall would be able to withstand the water pressure.
Does the atmospheric pressure increase or decrease at a height above sea level ( eg. mountain)
The atmospheric pressure decreases as fewer particles push down on us.
How does tropical cyclones occur due to atmospheric pressure?
When the sun warms the water on the oceans on the ocean surface, the water at the surface gains heat and evaporates. The warm water vapour rises, creating an area of lower pressure near the ocean surface. Air from the surrounding area of higher pressure flows into the area of lower air pressure. The process repeats itself and the differences in air pressure over the ocean causes storms to develop.
