p2.3-Forces in Action Flashcards
p2.3.1-How do you change the shape of an object?
Forces can compress, stretch or bend objects and you need more than one force to do this. Some materials stretch, but don’t return to their original shape when you remove forces which are plastic. Many are elastic though which do return to the original shape when you remove forces.
p2.3.1-What happens when you stretch a spring?
Force and extension of the spring have a linear relationship up to where they stop which is the limit of proportionality. The elastic limit is the point at which if you remove the force, the spring returns to original length. Above the elastic limit doesn’t return to the original shape as it’s permanently deformed.
p2.3.1-What are spring constant calculations?
Spring Constant(N/m) = force(N) / extension(m)
Energy transferred in stretching(J) = 0.5 x spring constant(N/m) x extension(m^2)
energy transferred is also work done
p2.3.2-What happens when you stretch other materials?
The graph for an elastic band shows there is a non linear relationship between force and extension. You can’t use an elastic band in a newtonmeter as it doesn’t obey hookes law so you use a spring. Materials become thinner when stretched and thicker when squashed.
p2.3.3-What is a gravitational field?
A gravitational field is a region where a mass experiences an attractive force. Gravitational field strength is a measure of the force on a 1kg mass when it is in a gravitational field due to another mass. Mass doesn’t change, but the force of the mass depends on the field and force is bigger if distance is smaller or mass is bigger.
p2.3.3-What is the weight?
Weight is what we call the force of the earth on an object when it is on the objects surface. It also refers to the gravity force of planets and other bodies in the universe and the effect this has on objects.
p2.3.3-What are gravitational field strength calculations?
Gravity force(N) = mass(kg) x gravitational field strength(N/kg)
Resultant force(N) = mass(kg) x acceleration due to gravity(m/s^2)
Gravitational potential energy(J) = mass(kg) x height(m) x gravitational field strength(N/kg)
p2.3.4-How do force cause rotation?
The legs of your chair act as a pivot. The force acting on you when you lean back acts on certain distances so the chair turns. This is a turning effect or moment. It is more difficult to produce a turning effect when the force acts closer to the pivot.
p2.3.4-What is the principle of moments?
You can balance a see-saw if the people on the see-saw sit in the right places. An object is balanced if the anti clockwise moments are equal to clockwise moments about the pivot.
moment of a force = anti clockwise moment = clockwise moment
moment of a force(Nm) = force(N) x distance(m)
p2.3.5-How do levers transmit forces?
A lever is a force multiplier which transmits forces by rotating about a pivot. The effort is the force that you exert on the lever. The load is the force that the lever exerts on the body. If the pivot is close to the load, then you only need a small effort to lift it. The ratio of the load to the effort is the mechanical advantage.
p2.3.5-How do gears transmit forces?
Gears are like levers that rotate. If you make a small cog rotate with a certain force, it will make the larger cog rotate. The bigger cog exerts a bigger force, but won’t move so far. The ratio of diameters of cogs tell you the ratio of the effort and the load. You can use the gears to change the direction or the rotating force.
p2.3.5-What are mechanical advantage calculations?
Mechanical advantage = load(N) / effort(N)
effort(N) = load(N) x distance from pivot to load(m) / distance from pivot to effort(m)
p2.3.6-What is a hydraulic machine?
It is a machine that uses a liquid to transmit a force. It is made of two pistons connected by a pipe. When you push on one piston, the pressure is transmitted through the liquid and the other piston moves.
p2.3.6-What are pressure equations?
pressure (Pa) = force normal to surface(N) / area of that surface(m^2)
force x area / area = pressure x area
