Force, Mass, and Motion

Brad and Erin decide to have a tug of war contest. Erin pulls the rope with all her might and so does Brad. Sadly, Brad only pulls with half the force that Erin pulls with.

Which way will the rope move?

• Towards Brad, since the forces are balanced.

• Towards Erin, since the forces are unbalanced.

• Towards Erin, since the forces are balanced.

• Towards Brad, since the forces are unbalanced.

Tags

NGSS.MS-PS2-2

Consider the free-body diagram. If you want the box to move, the force applied while dragging must be greater than the

• force of gravity.

• tension force.

• normal force.

• friction force.

Tags

NGSS.MS-PS2-2

The Smith family is travelling in their car at 50 km/h due east. Mr. Smith is using cruise control to maintain a constant speed. Describe the net force acting on the Smith car.

• There is no way to determine net force.

• Net forces are unbalanced.

• Net force is positive and to the east.

• Net force equals zero.

Consider the four free body diagrams. Free-body diagrams are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation. Do any of the free body diagrams indicate motion? If yes, which one(s). Explain.

• No. In each case, the forces are balanced.

• Yes. In B the book is slowing down because of the friction force opposing motion.

• Yes. In B and D. In both cases, there is a net force.In B, there is a net force to the left; in D there is a net force upward.

• You cannot tell if there is any motion. You can only determine how much force is acting on the objects.

Tags

NGSS.MS-PS2-2

The law of inertia states that an object in motion will stay in motion, and an object at rest will stay at rest unless acted upon by an unbalanced force. Which law of motion is this describing?

• Newton's Second Law

• Newton's Third Law

• The law of gravity

• Newton's First Law

The image above shows two opposite forces acting on a rope, what can we say is true about the affect of the forces on the rope?

• The forces are unbalanced, and net force on the rope moves it to the right.

• It cannot be determined because one man is standing taller than the other.

• It cannot be determined without knowing which man is stronger.

• The forces are unbalanced, and net force on the rope moves it to the left.

Two platoons line up for a tug of war. If both platoons have the same number of participants on a team, what other factor is critical to either platoon's win?

• height of men

• total mass of the team

• age of men

• condition of the ground

Tags

NGSS.MS-PS2-2

Jawanda was playing with her new Superman bobble head. She noticed that after she pushed Superman's head it would vibrate, but after a while it would bobble less and then stop. Which of Newton's laws best explains why this happened?

• The third law - The head is reacting to a action force.

• The first law - The head moves until a force stops it.

• The first law - The head is in motion and it will remain in motion.

• The second law - The head was not pushed hard enough to keep the head moving.

Forces that are equal in strength and opposite in direction are

• balanced forces.

• always result in motion.

• always the result of motion.

• unbalanced forces.

Consider the free body diagram. If the sum of the tension forces is equal to the force of gravity, which description best applies

• A book is at rest on a tabletop.

• A physics student rests a backpack upon one shoulder.

• A girl hangs by both hands, motionless, from a trapeze.

• A book is at rest on a tabletop.