Question

how forces affect motion
while objects move relative to one another, they can also speed up, slow down, and change direction. the motion of an object can change when one or more forces act on the object. a force is a push or a pull. when one object pushes or pulls another object, the first object exerts a force on the second object. you exert a force on a book when you push it into your book - bag. you exert a force on the sleeve of your jacket when you pull it off your arm.
describing force a force is described by its strength and by the direction in which it acts. the force needed to lift a dinner plate requires less strength than the force needed to push a refrigerator. pushing a faucet handle to the left is a different force from pushing it to the right. in an image, the direction and strength of a force acting on an object can be represented by an arrow. the arrow points in the direction of the force, as shown in figure 3. the length of the arrow indicates the strength of the force - the longer the arrow, the greater the force. in the international system of units (si), the unit for the strength of a force is called a newton (n), after the scientist sir isaac newton.

1 a bird sits on top of an elephant.

2 a horse starts pulling a man in a buggy.

3 a cat pushes a dog.

representing forces
figure 3 in the first image, a short arrow in a downward direction shows that the bird is exerting a small downward force on the elephant. draw arrows on the other images to represent the size and direction of the forces applied by the animals in action.
ccc cause and effect which image shows a force that causes a change in motion? why does this force cause a change in motion, but the forces in the other images do not?

Explanation:

Step1: Analyze Image 1

The bird sitting on the elephant exerts a small downward - force. But the elephant's motion doesn't change as the force is balanced by the normal force from the ground.

Step2: Analyze Image 2

The horse pulling the man in the buggy causes the buggy (and the man) to move. The horse's pull is an unbalanced force that overcomes any resistive forces (like friction) and changes the state of motion of the buggy from rest to motion.

Step3: Analyze Image 3

The cat pushing the dog might not cause a noticeable change in the dog's motion if the dog resists or if the cat's force is not strong enough to overcome static friction or the dog's own muscular resistance.

Step4: Determine the answer

The image that shows a force causing a change in motion is Image 2. The horse's pull is an unbalanced force that initiates the motion of the buggy. The forces in Image 1 are balanced (bird's weight and ground's normal force on elephant), and in Image 3, the cat's force may not be sufficient to overcome opposing forces on the dog.

Answer:

The image that shows a force causing a change in motion is Image 2. The horse's pull causes the buggy to start moving because it is an unbalanced force that overcomes resistive forces. In Image 1, the forces are balanced, and in Image 3, the cat's force may not be enough to overcome opposing forces on the dog.