Let us first guess the answer based on our commonexperience. To move a football at rest, someone must kick it.To throw a stone upwards, one has to give it an upwardpush. A breeze causes the branches of a tree to swing; astrong wind can even move heavy objects. A boat moves in aflowing river without anyone rowing it. Clearly, some externalagency is needed to provide force to move a body from rest.Likewise, an external force is needed also to retard or stopmotion. You can stop a ball rolling down an inclined plane byapplying a force against the direction of its motion.In these examples, the external agency of force (hands,wind, stream, etc) is in contact with the object. This is notalways necessary. A stone released from the top of a buildingaccelerates downward due to the gravitational pull of theearth. A bar magnet can attract an iron nail from a distance.This shows that external agencies (e.g. gravitational andmagnetic forces ) can exert force on a body even from adistance

Gravity can make a ball roll downhill without touching it. Kicking a ball can make it roll by touching it with a foot.To make something that is sitting still start moving, there always needs to be _______ on the object. A. light B. force C. heat D. contact

We can draw arrows to show the forces acting on an object. The length of an arrow indicates the size of the force. Its direction indicates the direction of the force.Two forces act on the soccer ball on the right:The Earth's gravity pulls it down.The person's hand pushes it up. This is called an applied force – a force exerted on the object by a person, animal or machine. (If you doubt this force exists, try holding a soccer ball like this for an hour!)The ball is motionless and is not accelerating, so the two forces must be equal and opposite.Another way of showing the forces acting on an object is to draw a free body diagram. A square represents the object, and arrows pointing out from the square represent the forces acting on it.These diagrams make it easy to calculate the net force. In the example, the arrows are equal in length but point in opposite directions. These forces are balanced, so the net force is zero.Question 1SavedLook at the free body diagram for the soccer ball above. Explain how you can tell that the net force on the ball is zero.

What property of an object in motion must be overcome before it can be brought to rest?

Charlie throws a ball up into the air. While the ball is airborne, which is the greatest force acting on the ball to slow it down?

When falling from a high building it is advisable to roll as you contact the ground.  Compared to contacting the ground and not rolling (assuming you fall from the same height), the purpose of this action is to:Question 22Select one:a.apply a smaller impulse to your body to change its momentum by decreasing the force appliedb.apply a larger impulse to your body to change its momentum by increasing the time over which the force is appliedc.apply the same impulse to your body to change its momentum by increasing the time over which the force is experienced and thereby decreasing the forced.apply a smaller impulse to your body to change its momentum by increasing the time over which the force is experiencede.apply the same impulse to your body to change its momentum by decreasing the time over which the force is experienced and thereby increasing the force