S8P3b- Balanced and Unbalanced Forces

A train rolls to a stop along a horizontal track without the conductor applying the brakes. What answer choice BEST explains why this occurred?

• The train ran out of momentum.

• The opposing force of friction stopped the train.

• The natural state of the train is not to be in motion.

• The force of gravity slowed the train until it stopped.

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 First Law

• Newton's Third Law

• The law of gravity

• Newton's Second Law

An object in motion will stay in motion unless acted upon by what type of force?

• balanced

• electrical

• magnetic

• unbalanced

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.

• Net force equals zero.

• Net forces are unbalanced.

• Net force is positive and to the east.

• There is no way to determine net force.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

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.

Since the forces are unbalanced the rope will move towards Erin. Using Newton's first law of motion as a model, explain how Brad could keep from losing the tug of war.

• Ask Erin to let go of the rope.

• Make the rope longer so Brad can get a better grip.

• Let Sarah, who pulls just as hard as Brad, team up with him to pull the rope together.

• Let Sarah, who pulls just as hard as Brad, team up with Erin to pull the rope together.

Tags

NGSS.MS-PS2-2

Your teacher was given an apple by a student trying to get on her good side. It sits on her desk the whole year, not moving.

You know that, if the apple were to roll off the desk, it would fall to the ground. So what is keeping the apple motionless on the desk?

• Once placed on the desk, gravity is no longer acting on the apple.

• The downward force of gravity on the apple is balanced by a larger force on the apple by the desk.

• The downward force of gravity on the apple is balanced by an equal but opposite force on the apple by the desk.

• The downward force of gravity on the apple is balanced by an equal but opposite force on the apple by the teacher.

Tags

NGSS.MS-PS2-4

Forces that are equal in strength and opposite in direction are

• balanced forces.

• unbalanced forces.

• always result in motion.

• always the result of motion.

When a moving object is acted on by unbalanced forces, the object will

• stop moving.

• move in unpredictable patterns.

• move in the same direction as the stronger force.

• move in the direction opposite the stronger force.

Tags

NGSS.MS-PS2-2

Julio hit a baseball. What caused the ball to change direction at the time of impact?

• the force of gravity

• the speed of the ball

• the force of his swing

• the weight of the air

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

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?

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

• The forces are not balanced, because one man is standing taller than the other.

• The forces are balanced. But, the forces acting on the rope have increased and the rope’s motion is affected.

• The forces are balanced. Thus, there is no change in forces acting on the rope and the rope’s motion is not affected.