3.1 Uniform Gravitational Fields Flashcards
What is a gravitational field?
a region where a mass feels a force
What kind of a force does a mass feel in this region?
A non-contact one
Objects of what interact through gravitational field?
of a mass
What does the gravitational field of the sun do?
Keep the planets around it in orbit , by its gravitational ‘pull’
Do humans experience a gravitational pull by the earth?
Yes, due to the force called weight (as we have mass)
Why do object with a greater mass have a more significant effect on gravitational fields?
As the force felt/provided depends on the mass
Any object with a mass will experience a force of what if put within a force field of another object (gravitational field).
of gravitational attraction
can gravitational force be both attractive and repulsive?
No, only attractive
What do we assume about the gravitational field strength near the surface of the earth?
We assume it is constant and hence we assume the gravitational field is uniform?
What is the gravitational field strength defined as?
Gravitational force per unit mass acting on a mass at that point in the field
What is the equation for gravitational field strength?
g = F / m g = gravitational field strength (Nkg^-1 or kgms^-2) F = gravitational force (N) m = mass (kg)
what is gravitational field strength approx. at earth’s surface?
9.81 Nkg^-1
is gravitational field strength a vector or a scalar?
Vector, it always points towards the centre of mass creating the field
Is the gravitational field pointing in the same direction as the force it exerts on objects of mass?
Yes
What else can gravitational field strength be taken as near earth’s surface?
The acceleration, since F = ma
What is this acceleration often called?
Acceleration due to gravity
Is the gravitational field of the earth actually uniform?
No, it is radial but along the surface the change in strength is so little that we consider it to be uniform
Does the value of gravitational field strength vary around the world?
Yes, as the earth is not an exact sphere
In terms of gravitational potential what is the magnitude of it at earth’s surface?
0, it is said to be an equipotential surface
When moving along a equipotential what doesn’t happen?
The work isn’t done
What is an equipotential
Region of equal potential
Moving from one equipotential to other causes what?
A change in gravitational potential energy (gpe)
How do we work out the change in gravitational potential in a uniform field?
g x change in distance
it gives units of Jkg^-1
Why are the units Jkg^-1
as gravitational potential is defined as potential energy per unit mass
So to work out the change in GPE what do we need to do to equipotential value?
Times it by the mass of the object