Gravity
Newtons per Kilogram
What are the units of gravitational Field strength?
Joules per _____ = units of electric potential
Coulomb
Sketch the curve of potential difference across a capacitor as it is charging against time
Exponential increase, levelling off at V0
Define gravitational potential
The work done per unit MASS to bring a test mass from a point infinitely far away to that point in the field.
Define Electric potential
Work done per unit charge to bring a small POSITIVE test charge from a point infinitely far away to that point in the field.
The initial potential difference across a capacitor is V0. The capacitor discharges through a circuit of time constant T.
What is the Pd after 2 time constants
V0/e2
_____=GMm/r
What is the equation for Gravitational Potential?
What is Coulomb's Law
F=kQq/r^2
What physical factors can be changed about a capacitor to increase its capacity
Increase Area
Reduce distance between plates
Dieletric permittivity
A rocket of mass 2500Kg is on the surface of the Earth. If it is flung from the Earth at a speed of 10Km/s, will it escape the Earth's gravitational field?
Mass Earth = 6x10^24 Kg
Radius Earth 6400 Km
Kinetic Energy < Gravitational potential energy on surface of the Earth.
Therefore it won't leave the field.
A small object of mass m has a charge Q. The object remains stationary in an evacuated space between two horizontal plates. The plates are separated by a distance d and the potential difference between the plates is V.
What is V?
V = mdg/q
A capacitor of capacitance 120 μF is charged and then discharged through a 20 kΩ resistor.
What fraction of the original charge remains on the capacitor 4.8 s after the discharge begins?
0.14
A rocket of mass 2500Kg is on the surface of the Earth. If it is flung from the Earth at a speed of 5Km/s, what is the max distance above the surface of the Earth that the rocket will reach.
Mass Earth = 6x10^24 Kg
Radius Earth 6400 Km
KE = 3.125 x 10^10 J
Final GPE = 1.25 x 10^11 J
Largest distance from centre of earth = 8x10^6 m = 8000Km
Largest distance above surface = 1600 Km
In α particle with an initial kinetic energy of 4.9 MeV is directed towards the centre of a gold nucleus of radius R which contains 79 protons. The α particle is brought to rest at point S, a distance r from the centre of the nucleus as shown in the diagram below.
Calculate r, the distance of closest approach of the α particle to the nucleus.
r = 4.67 × 10−14 m
Initially a capacitor stores 600 µC of charge. When it loses half of this charge, the potential difference (pd) across it decreases by 50 V.
What is the capacitance of the capacitor?
6.0 µF