P5 - Resultant Forces And Work Done

Question 1

What do free body diagrams show?

Answer 1

All the forces acting on an object

Question 2

What are the different types of forces acting on an isolated object?

Answer 2

NO

Question 3

What forces are acting on a skydiver?

Answer 3

The skydivers weight act on him pullin him towards the ground but drag(air resistance) also acts on him, in the opposite direction to his motion

(You can show this in a free body diagram)

Question 4

What do the sizes of arrows show on free body diagrams?

Answer 4

The relative magnitudes of the foroes and the directions show the directions of the forces acting on the object.

Question 5

What is the resultant force?

Answer 5

Resultant Force is the Overall Force on a Point or Object

Question 6

Usually, how many forces are acting on an object?

Answer 6

Along any direction, there are at least 2 forces

Question 7

NOTE: For free body diagrams

Answer 7

If you have a number of forces acting at a single point, you can replace them with a single force loo long as the single force has the same effect as all the original forces together)

Question 8

What does it mean if forces all act along the same line?

Answer 8

They are all parralel

Question 9

How is the overall affect(resultant force) found in a free body diagram?

Answer 9

The overal affect is found by adding those going in the same direction and subtracting any going in the opposite direction.

Question 10

If a car has 1500N weight and 1500N normal contact weight, 1200N drag and 1000N backwards what is the resultant force?

Answer 10

1500N - 1500N = 0
1200N - 1000N = 200

The resultant force in 200N to the left

Question 11

What does it mean if the a force moves an object through a distance?

Answer 11

ENERGY IS TRANSFERRED and WORK IS DONE on the object

Question 12

How do you make an object move?

Answer 12

To make something move (or keep it moving if there are frictional forces), a force must be applied.

Question 13

What does the object applying the force need?

Answer 13

A source of energy

(Like fuel or food)

Question 14

What happens when a force does ‘work’ to move an object?

Answer 14

Energy is transferred from one store to another

Question 15

NOTE : About energy being transferred

Answer 15

Whether energy is transferred usefully’ (e.g. lifting a load) or is ‘wasted’ ,you can still say that work is done. This means ‘work done’ and ‘energy transferred’ are the same.

Question 16

What happens when you push a carpet against a rough surface?

Answer 16

When you push a carpet along a rough surface, you are doing work against frictional forces. Energy is being transferred to the kinetic energy store of the object because it starts moving. but some is also being transferred to thermal energy stores due to the friction. This causes the overall temperature of the object to increase. (Like rubbing your hands together to warm them up.)

Question 17

Equation to find out how much work is done

Answer 17

Work done (J) = Force(N) x Distance(m)

W = Fs

Question 18

When is one joule of work done?

Answer 18

when a force of one newton causes an object to move a distance of one metre.

( And as 1N = 1J this means 1J = 1Nm/newton meter)