Flashcards in Forces Deck (46)
What do vector quantities have? Examples?
-have a MAGNITUDE and DIRECTION
-force, velocity, acceleration, displacement, momentum
What do scalar qualities have? Examples?
-speed, distance, mass, temperature, time
What is a contact force?
When two objects have to be touching for a force to act
What is a non contact force?
When objects do not need to be touching to cause a force
How do you calculate the weight?
Weight= mass (kg) X gfs (N/kg)
What forces act on a car?
^ normal contact force
> driving force
How do you calculate work done?
Work done= force (N) X distance (m)
How do you calculate the elastic potential energy?
=0.5 x spring constant (N/m) x extension (m)
How do you calculate the moment of a force?
Moment = force X distance
How do you calculate pressure?
Pressure (Pa) = Force / Area (m2)
What does a lever do?
They increase the distance from the pivot at which the force is applied. This means less force is needed to get the same moment
What do gears do?
Different sized gears can be used to change the moment of a force
What does Newton's first law of motion state?
Objects with balanced forces acting on them will stay at rest or in constant motion
What does Newton's second law of motion state?
When an unbalanced force acts on an object, the direction of the objects acceleration is the same as the unbalanced forces direction.
F=mass x acceleration
What is friction?
A force that opposes motion when two objects slide past each other.
Why would a person weigh less on the moon?
Because the gravitational field strength of the moon is a lot smaller than that of earth. But our mass would stay the SAME
What does Newton's third law state?
The size of the forces acting on the first object equals that of the second object. In every interaction, there is a pair of forces acting on the two objects
How do you convert from Nm to joules?
1 joule = 1 Nm
Eg 5J = 5Nm
What happens when you apply a force to an object?
It will stretch, compress or bend
What happens when a spring is stretched or compressed?
Work is done which causes energy to be transferred to the elastic potential energy store of the object which is equal to the work done
If it is elastically deformed then ALL of this energy has been transferred to its epe store
How do you calculate the force of an object?
Force =Spring constant X extension
How do you investigate the relationship between the force and extension of springs? (PRACTICAL)
Measure the length of the Spring with a ruler when a weight is added. Continue this using more weights each time by hanging them.
How do you calculate the moment?
Moment (Nm) = force X distance
What is the moment?
The turning effect of a force (causes object to rotate)
What is the pressure of a fluid?
A force is exerted normal to any surface in contact with the fluid
What does it mean if a liquid is dense?
It means it has more particles in a certain space. Density is a measure of 'compactness' of a substance.
Density (kg/m3) =mass / volume
What is upthrust?
Force that determines whether an object will sink or float. It is a resultant force. An object will float if it's weight = upthrust.
What is atmospheric pressure?
The pressure exerted by the air around us. It is created on a surface by air molecules colliding with the surface
What happens as the altitude (height above Earth) increases?
The atmospheric pressure will decrease because the atmosphere becomes less dense so there are fewer air molecules able to collide with surface
Which is why cliffs have a low atmospheric pressure