Identify a force interaction

A force acts on an object

A force is a push or pull caused by an interaction. If a hand presses a sponge, the hand exerts a force on the sponge. The hand is the source of that force; the sponge receives it. Start with one named force, even when several forces act

1. 1Receiving object Ask: which object has this push or pull acting on it?
2. 2Source Ask: what object exerts this particular push or pull?
3. 3Follow the link For a cable pulling a cart, name cable → cart. The cart can also experience other forces

This picture shows only the cable pull on the cart. The arrow points in the pull direction, not necessarily the travel direction. The key names the source: cable. Which object receives this force?

Read the target object named above the cart. Source → receiving object is cable → cart

The same cable pulls the same cart more strongly. Does that alone change which object is the source and which receives the force?

Force strength is measured in newtons, written N. Move the cable pull from 1 N to 6 N, then back. Compare the arrow with the fixed 6 N reference and check the source and target labels. This is a drawing of one force, not an experiment measuring how far the cart moves; other forces and motion are not shown

What changes when you increase the cable pull?

Do the interacting objects need to touch?

A contact force needs the interacting objects to touch. A hand pushing a ball, a shelf supporting a book and air pushing a sail are contact interactions. Gravity and magnetic forces can act across a gap, so they are non-contact interactions

1. 1Air counts as contact Air touches a sail as it pushes, even though the air is usually invisible
2. 2No movement is needed A shelf can exert a support force on a stationary book
3. 3Find the immediate source If a hand pulls a rope attached to a sled, the rope pulls the sled. The hand pulls the rope; it does not touch the sled
4. 4Gravity across a gap Earth pulls on a ball above the ground. The ball does not need to touch the ground for gravity to act

A stretched elastic strap is attached to a toy car. A child holds the other end without touching the car. Consider the pull acting directly on the car. What exerts it?

Find the object attached to the car, not the person pulling at the far end

Falling rain pushes against an open umbrella. The person holding it also feels a force through the handle. Consider only the force exerted by the rain. What receives that force?

Which object is the rain pushing against in this interaction?

A foam block rests on a platform. Consider the platform’s upward support force and Earth’s downward gravitational force on the block. Which classification is correct?

The platform touches the block. Earth can attract objects even when they are above the ground

Explain the link in a short sentence

Example: “The shelf exerts an upward force on the book. This is a contact force because the shelf touches the book.” The explanation names the source, receiving object and evidence for the classification

1. 1Name both objects Saying only “support” names a force type, not the two interacting objects
2. 2Give relevant evidence Use touching or the ability to act across a gap. Do not use whether the object happens to be moving
3. 3Assessment limit You can practise saying or writing your own explanation, then compare it with this structure. The app does not automatically assess your own prose

A motor turns a conveyor belt. A crate sits on the belt and is carried along. The motor does not touch the crate. Consider the horizontal force applied directly to the crate. Which description identifies this interaction?

One force, two objects

Choose the receiving object, then identify what exerts the named force. Decide whether that interaction needs touching. A force arrow shows strength and direction, not distance travelled

1. 1Keep interactions separate Several forces can act on one object. Naming one force does not mean that all other forces vanish
2. 2What comes next Next we compare the directions and sizes of several forces on one object. This activity does not yet assess complete force diagrams or changes of motion
3. 3Activity, not mastery Finishing these guided checks records completion of this activity. The optional practice bank is finite and does not establish independent drawing, written explanation or practical competence