Balanced and unbalanced forces

Activities: use the following words to complete the sentences below.

direction, big, stopped, arrows, short, one, same, opposite, length, slow, drag, balanced, decrease, change, increases, speed, stationary

Representing forces

Scientists use _________ in diagrams to represent forces. The _____________ of the arrow shows which way the force is acting. The length of the arrow shows how ___ the force is. A long arrow represents a larger, stronger force than a ______ arrow. The arrows that represent forces acting on an object should be drawn from the object’s centre of gravity.

Balanced and unbalanced forces

Forces act on us all the time when we are moving and even when we are ____________. More than ____ force is acting on us all the time. The forces acting on us can be balanced or unbalanced.

Balanced forces

The arrows describing the up and down forces acting on the kayaker are the _________ length. This shows that the forces are the same size. But these forces are acting in _____________ directions. The force of gravity pulls down on the kayaker, but the buoyancy force of the water pushes up. The two forces are ________________ so the kayaker does not move up or down.

Unbalanced forces

The arrows describing the forward and backward forces on the kayaker are not the same ________. The forward force comes from the kayaker using a paddle to push forwards. The backward force is the _____ from the water slowing the kayak down. These forces are unbalanced. Unbalanced forces cause objects to ________ up, ______ down or __________ direction. The forward force is larger than the backward force, so the kayaker and his kayak move forwards faster and faster. Eventually they cannot move any faster because drag ___________ when speed increases.

The effect of balanced and unbalanced forces

Unbalanced forces cause things to start moving, like a kayak in the water. Unbalanced forces can increase or decrease the speed of the kayak as well. If the forward and backward forces are balanced, there is no increase or ____________ in speed; the kayak moves at a steady speed or remains _______________.