Unit 5

In Unit 5 we managed to cover these topics:

1. Work and Power
2. Work, Potential Energy and Kinetic Energy Relationship
3. Conservation of Energy
4. Machines

 

1.The equation for Work is "work = force*distance", work is measured in joules and can only be present if the force and distance are parallel, for example A person going up the stairs would have work because both the force and distance are upwards, but a person carrying a glass and moving forward, no force is acted on the glass as the force and distance are perpendicular. Example if you weigh 50 newton and run up a 10 meter high stairwell,  50*10 = 500J

 

Power is how fast work is done and is measured in Watts, the equation for power is "power = work/time". Example if you weigh 50 N and run up a 10 meter high stairwell in 5 seconds, 50*10 = 500, 500/5 =100 Watts.

 

2. Kinetic energy is the measurement of the energy carried by a moving object, it is like work also measured in Joules as the change in Kinetic Energy is equal to Work. The formula for Kinetic energy is KE = 1/2m(v^2). How does an airbag keep us safe ?

You always go from moving to not moving weather and airbag is present or not. this means Kenetic Energy will be the same in both. Airbags only increase the distance it takes which decreases the force making you suffer less injury but the work is still the same.

Potential Energy is the energy of a position (height). The equation for Potential Energy is PE = mgh which is mass*gravity*height. PE can be present while an object is at rest or moving. Potential energy can change into Kinetic energy when it goes from falling to hitting.

 

3. Energy Cannot be created nor destroyed they simply convert from one form to another, this is called conservation of energy. Example in Newton's cradle as one ball is lifted you just put some potential energy in it, when you release the ball and it hits the other balls the energy is converted from potential to kinetic energy, as the ball from the other side pops up it converts back again into potential energy and so on.

 

4. Machines use work to operate, the work in always equals the work out. A machine works by increasing the distance thus decreasing the force needed to move the operate the machine, but the work always stays the same. Example: Xavier lifts a 200N box up into a truck that is 1 meter high from the ground and uses 200 Joules of energy to do so. Gannon on the other hands is smart and uses a 3 meter long ramp to push his box up,  his work will also be 200Joules but because the distance is 3 then the force = 67 which is way easier than what Xavier did.