4.5.1.4 Resultant Forces

Question 1

Resultant force:

Answer 1

A number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together. This single force is called the resultant force.

Question 2

What are the rules on how free body diagrams should be drawn?

Answer 2

• Draw objects as a circle
• Draw arrows away from object
• Label force acting on object
• Arrow length shows us the size of the force
• Direction of the arrow is the direction of the force
• Don’t draw surrounding objects
• If object is stationary or moving at a steady/constant speed then the arrows would be the same length

Question 3

What is the difference between free body diagrams and force diagrams?

Answer 3

• free body diagrams are only supposed to focus on one object and the forces acting on it not the objects it’s interacting with
• the object the forces are acting on is shown as a circle or square rather than the actual object being sketched out

Question 4

Force Diagram Example:

Answer 4

Question 5

Free body diagram to show an aeroplane moving at a constant velocity and altitude from the ground:

Answer 5

Question 6

Free body digram to show masses hanging from a string:

Answer 6

Question 7

Free body diagram to show a levitating paperclip:

Answer 7

Question 8

Free body diagram to show a ball in water:

Answer 8

Question 9

Free body diagram to show a book resting on a table:

Answer 9

Question 10

Free body diagram to show a cupcake case falling through the air at a steady pace:

Answer 10

Question 11

Free body diagram to shown an aeroplane accelerating:

Answer 11

Question 12

Free body diagram to show a block on a slope:

Answer 12

Question 13

Steps to combine forces into one resultant force:

Answer 13

1. Calculate resultant horizontal and vertical force.
2. Tip to tail arrows - have a starting point.
3. Draw the resultant force with arrow (from start to finish).

Question 14

Steps to separate forces into horizontal and vertical forces - called resolving the force:

Answer 14

1. Horizontal and vertical tip to tail arrows.
2. Measure.

Question 15

Steps to find resultant force of forces at funny angles:

Answer 15

1. Measure the arrows for the magnitude and direction of each force.
2. Draw out force arrow 1.
3. Draw out force arrow 2 at the tip of force arrow 1.
4. Draw and label the horizontal force.