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Balanced and unbalanced forces

Balanced forces

When an object is not moving the forces acting on the object are balanced.

weight force of the paddlers = support force of the waka

Qn 1: Is the waka moving? Are the forces balanced or unbalanced?

Qn 2: What do you think the relationship is between the person’s weight force and the support force of the waka? Are these forces balanced or unbalanced?

Qn 3: If two people sat in the waka, would the support force of the waka and the weight force of the people be balanced or unbalanced? Why?

Qn 4: What do you think would happen if seven people climbed into the waka? What changes would happen to the support and weight forces? Would these forces balanced or unbalanced?

When an object travels at a constant speed the forces are also balanced. If a waka ama team were paddling at 10km/hr (fast walking speed), the force of the paddles pushing against the water would be the same as the drag forces of the water pushing against the hull and the wind pushing against the people.

thrust force of the paddlers = drag force of water and wind

Unbalanced forces

When the forces acting on an object are unbalanced, the object will either accelerate or decelerate.

When a waka ama team start a race the thrust force from the paddlers will be much greater than the drag force of water and wind. This means that the waka ama will accelerate. Because the thrust force is greater than the drag force, the forces are unbalanced.

Measuring forces

We measure force using a unit called the newton or N for short. Ten newtons is equal to one kilogramme.

Qn 1: What is your weight force measured in newtons?

Qn 2: If you climbed into a waka ama, what would be the support force of the waka in newtons?

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