Balanced and Unbalanced Forces

No change = No net force acting.


What are balanced and unbalanced forces?

View the video on the right and answer the questions below.


1) A bird lands on a branch and remains motionless seating on the branch. The arrow pointing downwards represents the size and direction of the force of gravity due to the birds mass. Which one of the four force arrows represents the reaction force applied by the branch on the bird? Explain why you selected this arrow.


2) Two different birds now come and seat on the same branch and remain motionless. The direction and size of the force that each bird exerts on the branch is shown by arrows X and Y.
Which of the arrows A to D represents the force applied by the branch on the birds just before it snaps and the birds fly away. Explain your selection


3) A cyclist is traveling at constant speed along a footpath.

a. State the four forces acting on the cyclist?

b. Are these forces balanced? Explain your answer.



4) Two forces acting on the bike are shown on the right by the two white arrows. Which one of the following scenarios is most likely. Explain your answer.
i. The cyclist is using more force to push the peddles and the bike is getting faster.

ii. A strong head wind is blowing and pushing the cyclist backward.

iii. A tail wind has just blown up and pushing the cyclist forward.


5) The four forces acting on the cyclist are represented by white arrows shown on the right. Select from the following statements to describe the motion of the cyclist. Explain your selection.

i. The bike is slowing down.

ii. The bike is accelerating.

iii. The bike is traveling at constant speed.



6) Which combination of the following force arrows, from A to F, will cause the bike to travel at constant speed? Explain your answer


7) Which pairs of forces are balanced?


8) Describe the motion of the bike if forces A , F, C and E were acting on it


Download a Word doc of this exercise