Chapter 9 - Application Of Forces And Transfer Of Energy Flashcards
Name contact forces and non-contact forces
Contact forces - Friction and elastic force
Non-contact forces - gravitational force and magnetic force
Define friction
Friction is the force that OPPOSES MOTION between two surfaces in CONTACT.
Define elastic force
What is the direction of elastic force?
Elastic force is the force acting on a STRETCHED or COMPRESSED ELASTIC object to return to its ORIGINAL shape.
When an elastic material is stretched or compressed, it resists the change in shape by exerting a force in the [OPPOSITE DIRECTION]
When a planet exerts gravitational force on an object, the object is known to have _______
Weight
Weight is a _____, and its SI unit is _____
Force
Newton (N)
Define Magnetic force.
Why are maglev trains so fast?
It is the force exerted between a magnet and another magnetic material
As the maglev train travels on the track, the magnetic force of repulsion lifts it slightly above the track. This greatly reduces the friction between the train and the track, allowing the train to travel at a higher speed.
Define weight.
Define mass.
What is the SI unit of mass?
Weight is the measure of the [gravitational force acting on an object].
Mass is the [amount of matter in an object].
The SI unit of mass is kg
What can we use to measure weight,
And mass?
How does the measurement of weight,
And mass change?
We measure weight using a [spring balance], and mass can be measured using an [electronic balance] or a [beam balance].
The weight of an object may change with location, while the mass remains constant.
What effects does the transfer of energy between objects have on the object? It can:
-Move a stationary object
-Change the speed of an object
-Change the direction in which an object moves
-Stop a moving object
-Change the shape/size of an object
The [area of contact] affects the [pressure exerted] by an object.
A woman stepped on her phone. To her horror, the sharp heel of her high-heeled shoe cracked the screen of her phone. Why did this happen? What would have happened if the woman had been wearing sneakers?
The heel of a high-heeled shoe has a [small area of contact] with a [surface]. When the woman stepped on her phone, the screen cracked due to the [high pressure] that her heel [exerted] [on] the screen of her phone. However, a sneaker has a [higher area of contact] with a [surface] compared to a heel, and the screen will not crack as easily due to the [lower pressure exerted on it].
Define pressure.
Pressure is force per unit area.
What is the formula to calculate pressure?
P = force/area,
The unit of pressure is N/m2, also known as as the [pascal (Pa)]
What are factors affect the amount of pressure in liquids?
-Density of the liquid
-Depth of the liquid
What are factors affecting the amount of atmospheric pressure?
What do we use to measure atmospheric pressure?
The height above sea level. The greater the height, the lower the atmospheric pressure. This is an inverse relationship.
A barometer
How are we able to drink from straws?
How is a suction cup able to stick to a surface?
When we suck on a straw, air is removed from it. The [AIR pressure inside the straw decreases] and becomes [lower] than the [surrounding ATMOSPHERIC pressure]]. The [higher surrounding atmospheric pressure pushes] the liquid up the straw and into our mouth.
When we press a suction cup against a surface, [air is pushed ou] from under the suction cup. The [AIR pressure BETWEEN the suction cup and the surface decreases] and becomes [lower than the ATMOSPHERIC pressure]. The higher atmospheric pressure holds the suction cup in place.
