Forces and Electricity Flashcards
The area under an acceleration/time graph represents…
The velocity.
What must be done for projectile calculations at an angle?
The initial velocity must be resolved into its vertical and horizontal components.
Force down a slope is…
The horizontal component of the weight.
The normal reaction force of an object on a slope is…
The vertical component of its weight.
Define centre of mass.
The point of an object through which a single force would provide no turning force.
Newton’s first law.
Objects will remain at rest or constant velocity unless acted upon by a resultant force.
Newton’s second law.
The rate of change of momentum is proportional to the resultant force.
Newton’s third law.
If object A exerts a force on object B, then B will exert an equal and opposite force on A.
What happens in an elastic collision?
Kinetic energy is conserved.
What’s an Ohmic component?
One where current is directly proportional to potential difference. They obey Ohm’s law, so resistance is constant.
Threshold potential difference of a diode.
0.7V
Mains potential difference.
230V
Why do bulbs normally blow when they are first turned on?
- They are cold, so their resistance is low.
- As resistance is low, current will be high.
- Sudden high current means a rapid increase in temperature.
What’s a superconductor.
Materials that have zero resistivity. For this to happen, they must be really cold: ~10K.
Define critical temperature.
The exact temperature at which the resistivity of a materials becomes zero.
