# Force Daigrams

Questions: 1. Read each description below. Choose the force diagram (free-body diagram) that best represents the description. The forces are acting on the object in red type. You may neglect the effects of air resistance. | A. Mindy’s Christmas tree ornament hangs motionless on a tree. | B. Corey’s Christmas tree ornament is falling to the floor. | C. A ball thrown by Ginger is moving upward through the air. | D. A ball dropped by Melissa is falling downward toward the floor. | E. Matt’s book is motionless on a table. | F.

A ball that was thrown upward by Yvonne is at the top of its path. | 2. Read each description below. Choose the force diagram (free-body diagram) that best represents the description. You may neglect the effects of air resistance. | A. Mark’s physics book is on the desk. Mark pushes horizontally (from the side) on the book, but the book does not move. | B. Kendall’s physics book is on the desk. Kendall pushes horizontally (from the side) on the book, and the book moves across the desk at a constant speed. | C. Jenny pushes a cart at constant velocity down the grocery store aisle. D. Eddy is driving his Camaro down a straight, level road while on cruise control. | E. Ryan is accelerating his Dakota down a straight, level road. | F. Jackie’s Viper is parked on the shoulder of the road while she changes a flat tire. | 3. Paul Hewitt poses this question in his book: “If the forces that act on a bullet and the recoiling gun from which it is fired are equal in magnitude, why do the bullet and gun have very different accelerations? ” Think about Newton’s Second Law (F = ma) to answer his question. Source: © 1997 Paul Hewitt, modified by FLVS] The mass of the bullet is lower than the mass of the gun causing the bullet to have a greater acceleration than the gun according to newton’s third law of motion. 4. Jessica’s weight is 540 Newtons. According to the Third Law, if the Earth pulls on Jessica with a force of 540 N, then Jessica pulls on the Earth with a force of 540 Newtons that acts in the opposite direction. However, if Jessica stumbles while rollerblading, she will fall down to the ground. Explain why this happens.

The mass of the Earth is much greater than the mass of Jessica so when an equal force is acting on two greatly differing masses, the greater mass will win every time. Therefore, she’s been acted on by an outside force because Newton’s First Law states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force and also Newton’s third law states that for every external force that acts on an object there is a force of equal magnitude but opposite direction which acts back on the object which exerted that external force. |