Resultant Forces And Work Done Flashcards
What do free body diagrams show?
-Free body diagrams display all the forces acting on an object or system, excluding any forces the object or system exerts on the surroundings
-the sizes of the arrows show the relative magnitude while the directions show the direction of the force acting on the object
Use this free body diagram of a sky diver to describe what forces are acting on him
-The skydiver’s weight acts on him pulling him towards the ground
-drag (air resistance) also acts on him, in the opposite direction to his motion
What is a resultant force?
A single force that replaces multiple forces acting on an object, having the same combined effect as all the original forces.
How are resultant forces calculated when forces act along the same line (when they’re all parallel)?
When forces act along the same line, the resultant force is found by adding forces in the same direction and subtracting forces in the opposite direction.
For the free body force diagram given, calculate the resultant force acting in the van?
1)Consider the horizontal and vertical directions separately.
2)State the size and direction of the resultant force.
Vertical: 1500 - 1500 = 0 N
Horizontal: 1200 - 1000 N = 200 N
Answer: The resultant force is 200 N to the left.
What happens when a force moves an object through a distance?
energy is transferred, and work is done on the object.
What is required to make something move?
To make something move, or to keep it moving against frictional forces, a force must be applied, requiring a source of energy such as fuel or food
What is the relationship between work done and energy transferred?
-Work done and energy transferred are synonymous.
-Whether energy is transferred ‘usefully’ or ‘wasted’, work is still done.
How is work done against frictional forces explained?
-When pushing something along a rough surface like a carpet, work is done against frictional forces
-Some energy is transferred to the object’s kinetic energy store, causing it to move, while some is transferred to thermal energy stores due to friction, increasing the overall temperature of the object.
How do you calculate work done?
How many joules is in 1 Newton Meter?
1J=1Nm