Which model shows the structure and movement of particles in a solid? (a)  

• Model 1
• Model 2
• Model 3
• Model 4

Answer explanation

Model 2 shows particles that are held in a fixed position giving the substance a definite shape and volume.

Tags

NGSS.MS-PS3-4

A group of students is investigating the different factors that affect the strength of an electric motor. A diagram of the motor is shown. What step should the students take next in the investigation to increase the strength of the motor?

• Reduce the size of the axle running through the center of the motor.

• Increase the number of coils of wire within the two sections of the motor.

• Decrease the voltage of the power source being used to operate the motor.

• Place the permanent magnets and coils of wire farther apart inside the motor.

Answer explanation

To increase the strength of ANY electromagnet:

1. Increase the voltage of the electrical current.

2. Increase the strength of the magnet.

3. Increase the coils of the solenoid.

4. Move the magnets and coils closer together.

Tags

NGSS.MS-ETS1-1

NGSS.MS-ETS1-2

NGSS.MS-PS2-3

A force diagram of a tennis ball flying through the air toward the right is shown in the diagram below. The arrows show the direction of the gravitational force (F grav), the drag force (Fdrag), the lift force (Flift), and the direction of movement of the tennis ball. Which pair of statements is a valid description and explanation of the motion of the ball based on evidence from the diagram?

• description: The ball slows down as it moves to the right because the horizontal forces are unbalanced, with the larger force acting to the left. explanation: The ball speeds up as it moves downward because the vertical forces are unbalanced, with the larger force acting downward.

• description: The ball speeds up as it moves to the right because the horizontal forces are unbalanced, with the larger force acting to the right. explanation: The ball speeds up as it moves downward because the vertical forces are unbalanced, with the larger force acting downward.

• description: The ball moves at a constant speed to the right because the horizontal forces are unbalanced, with the larger force acting to the left. explanation: The ball slows down as it moves downward because the vertical forces are unbalanced, with the larger force acting upward.

• description: The ball slows down as it moves to the right because the horizontal forces are unbalanced, with the larger force acting to the right. explanation: The ball moves at a constant speed downward because the vertical forces are unbalanced, with the larger force acting upward.

Answer explanation

Since there is no force vector indicating a constant force applied to the right, the horizontal forces are unbalanced so the tennis ball will slow down.

The vertical forces are unbalanced, therefore the ball will accelerate due to gravity.

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-4

A coach at a track meet measured the time of a runner every 10 meters (m) during a 100 m dash. The data for the runner are shown. Which statement is the BEST analysis of the data for the runner?

• The runner covers the first 80 m running at a constant speed and then slows down, reaching a minimum speed during the final 20 m.

• The runner starts slower and speeds up, reaching a constant speed between 20 and 80 m, and then speeds up again during the final 20 m.

• The runner covers the first 70 m running at a constant speed and then speeds up, reaching a maximum speed during the final 30 m.

• The runner starts slower and speeds up, reaching a maximum speed between 50 and 70 m, and then slows down during the final 30 m.

Answer explanation

The runner starts slower and speeds up, reaching a maximum speed between 50 and 70 m, and then slows down during the final 30 m.

Tags

NGSS.MS-PS3-1

A force diagram for a down hill skier is shown. Use the diagram, Newton's Laws of Motion and the drop down menus (choices) to explaining the skier's speed.

The skier's speed increases going down the hill because forces (F1 and F2 or F3 and F4) are (balanced or unbalanced) and acting (perpendicular to or in the same direction as) the direction as the velocity, which causes the speed to change.

• F1 and F2, balanced,

  perpendicular to

• F3 and F4, balanced, perpendicular to

• F1 and F2, unbalanced, in the same direction as

• F3 and F4, unbalanced, in the same direction as

Answer explanation

"F3 and F"4 is the correct response for the first menu because the F1 and F2 forces are equal, and therefore are balanced, so these two forces will have no net effect. "Unbalanced" is the correct response for the second drop-down menu because balanced forces do not result in a change in speed. "In the same direction as" is the correct response for the third drop-down menu because again, the F3 and F4 forces are the forces that will affect the velocity down the hill.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

During a shot put event, athletes throw a very heavy round ball, called a shot, as far as possible. The graph shows the vertical velocity of a shot that was thrown by an athlete. Which statement is an accurate analysis of the vertical motion of the shot?

• The direction of the velocity is upward for both the first second and the last second, and the acceleration remains constant for the entire period.

• The direction of the velocity is downward for both the first second and the last second, and the acceleration decreases during the entire period.

• The direction of the velocity is upward for the first second and then downward for the last second, and the acceleration decreases during the entire period.

• The direction of the velocity is upward for the first second and then downward for the last second, and the acceleration remains constant for the entire period.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

NGSS.MS-PS2-4

A student is planning an investigation to explore different properties of matter. Which investigation will help the student explore a physical property of matter?

• investigation: Place a solid in a beaker and add a small amount of liquid. observation: The beaker becomes warm to the touch.

• investigation: Add a small amount of solid to a liquid in a beaker. observation: The solid dissolves in the liquid.

• investigation: Add a small amount of solid to a liquid in a beaker. observation: The solution starts to fizz and overflows the container.

• investigation: Place a solid in a beaker and add a small amount of liquid. observation: Bubbles form on the top of the solid.

Answer explanation

An unexpected temperature change and gas bubbles forming/fizzing are all indicators of a chemical change.

DISSOLVING is the process by which mixtures are made, so this is a physical change.

Tags

NGSS.MS-PS3-4

Iron can be found as a gray powder, and sulfur can be found a yellow powder. The diagram shows atomic models of two substances made of iron (Fe) and sulfur (S). Choose the correct table that you would have dragged and dropped into the table.

• 
• 
• 
• 

Answer explanation

This is the correct response because Model 1 shows a heterogeneous mixture where the particles retain their individual identities, so their different colors show. Model 2 is a pure substance because the pictures indicate the particles are combined to form a compound. A pure substance will have a uniform color throughout.

Tags

NGSS.MS-PS1-1

A student is shown a simple model of particles that make up a liquid, as shown. Part A How should the model be changed to show the particles of a solid?

• Increase the velocities of the particles, and increase the space between the particles.

• Increase the velocities of the particles, and decrease the space between the particles.

• Decrease the velocities of the particles, and increase the space between the particles.

• Decrease the velocities of the particles, and decrease the space between the particles.

Answer explanation

The change to a solid would require a removal of thermal energy from the system and

With less thermal energy the particles would slow down and when they reach freezing point begin to form more bonds.

Tags

NGSS.MS-PS1-4

A student is shown a simple model of particles that make up a liquid, as shown. Part B How should the model be changed to show the particles of a liquid at a higher temperature?

• Separate the particles into positive and negative charges, and increase the space between the particles.

• Separate the particles into positive and negative charges, but maintain the same space between the particles.

• Decrease the velocities of the particles, and decrease the space between the particles.

• Increase the velocities of the particles, but maintain the same space between the particles.

Answer explanation

The change to a solid would require a removal of thermal energy from the system and

With less thermal energy the particles would slow down and when they reach freezing point begin to form more bonds.

Tags

NGSS.MS-PS1-4