Task 1Contact ForcesIn this task, you'll explore three contact forces exerted by surfaces of objects.Estimated time to complete: 15 minutesYou will need these materials:safety gogglescleared space on a smooth, durable table that is at least 3 feet in length12-inch rulerball made of a hard material, such as a baseball, tennis ball, pool ball, lacrosse ball, whiffle ball, or ping-pong balllarge, heavy book or box to use as a barrierpiece of plastic or wood with a broad flat surface, such as a three-ring binder or a cutting boardarea rug, carpet, or piece of fabric with napAlways wear your safety goggles.Part ASet the ball and the barrier about two feet apart on the table. Grasp both ends of the ruler. Push the ball using the center of the ruler so the ball rolls, hits the barrier, and rebounds from it. Describe the motion of the ball as it moves.Part BIdentify the forces exerted on the ball from the time the ruler touches it.Part CQuestionThe force of the ruler on the ball is called an applied force. The force of the barrier on the ball is called a normal force. Both of these forces are exerted by surfaces, and the direction of force is at a right angle to the surface. The difference is that an applied force is exerted by a moving object and a normal force is exerted by a stationary object. Draw two arrows to represent the applied force and the normal force on the ball.Part DNow explore friction force. Set the piece of plastic or wood on the table and push it steadily across the tabletop using your fingertip. Note how much opposition to your push you feel. Repeat the steps, but this time push the piece of plastic or wood across a rug, carpet, or piece of fabric. If you're using fabric, be sure to secure the fabric so it doesn't move. How does the opposition to motion on the tabletop compare with that of the rug, carpet, or fabric?Part EFriction force is the opposition to the motion of surfaces sliding across each other. Based on your observations, what is one factor that affects the amount of friction?Part FQuestionDraw an arrow to represent the friction force.Part GList several examples of applied force, normal force, and friction that you've observed in your life.
