Everything in our world moves. Although you may not notice it, the world around you is constantly in a state of motion. The whirling wind causes the leaves on a tree to quiver. The ocean waves lift the surfer high above the tide. The baseball flies into the stands after being knocked out of the park by the batter. An object's motion will always change when acted upon by an unbalanced force.
For an object to move, forces need to act upon it. The force can speed up (accelerate), slow down (decelerate), or make the object stationary. Take the force of gravity, for example. Gravity keeps your textbook from floating off your desk. It keeps you from floating away into space when you do jumping jacks during physical education class.
An example of acceleration is bike riding. When you push down on the bike pedals, your weight forces the wheels to turn. You accelerate and go full speed ahead. Likewise, when a football player punts a ball, the force that he uses to make a powerful kick causes the ball to fly high in the air. A force that pulls or pushes in a different direction is called an opposing force. These cause an object to decelerate or stop. One example is when you take a dog for a walk. If the dog starts to chase a cat, his forward motion would be stopped by your pull on the leash. This principle is true with a tennis match as well. Both players are trying to keep the ball from going out over the back line. They stop the forward movement of the ball by hitting it with their racket. The rest of the force of the swing makes the ball change direction and fly back over the net.
A change in an object's movement as a result of a force can be described in terms of inertia. Inertia is an object's tendency to resist a change in motion. This concept of inertia is also referred to as Sir Isaac Newton's first law of motion. All objects have inertia. As an object's mass increases, its inertia increases. You need a larger force to overcome this larger inertia. For example, when you push a shopping basket, the basket will move in the direction of the force. It will continue to move as long as you push it. The greater the force used, the greater the change in the basket's motion. The greater the mass of the basket, the greater the force needed to cause a change in its motion.
Think about forces the next time you are playing softball or football with your friends. Remember, if you exert a greater force upon the ball, it will move faster and harder. Share this with your entire team, and you will be sure to win!
QUESTION 1
Complete the following analogy:
PEDALING A BIKE : ACCELERATION :: PULLING A DOG'S LEASH : _____.
OPTIONS
ENERGY
GRAVITY
INERTIA
DECELERATION
QUESTION 2
What is the meaning of the word stationary as used in the second paragraph?
OPTIONS
To shake
To fall
To remain in place
To pull down
QUESTION 3
The greater the mass of an object, the more ________ is needed to move it.
OPTIONS
help
force
energy
time
QUESTION 4
Which of the following is an example of an opposing force?
OPTIONS
Gravity pulling a ball down a hill
Wind blowing a leaf off of a tree
Gravity holding a rock still on the ground
Water pushing against someone as they wade through a pool
QUESTION 5
During a game of tug-of-war, the first team exerts a force of 3,500 N to the left. The second team exerts a force of 3,800 N to the right. Which of the following statements is true about the game?
OPTIONS
The forces are balanced, and there will not be a winner.
The forces are balanced, and the first team will win.
The forces are unbalanced, and the first team will win.
The forces are unbalanced, and the second team will win.
1 answer
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