Praxis Middle Science

Which of the following is an example of Newton's law of inertia?

• The force of a bowling ball on the pins equals the force of the pins on the ball.

• A bowling ball continues rolling down the bowling lane until it strikes the pins

• The weight of a bowling ball is directly proportional to its mass.

• 
  The force on a bowling ball by a person's hand is proportional to its mass and acceleration.

Answer explanation

Newton's law of inertia states that an object in motion will continue in its motion without change unless acted upon by an external force. The ball continues to roll at constant speed until its motion is changed by the pins.

The graph gives the position of x, an object, from t = 0 seconds, to t = 15 seconds. Which statement is true about the motion of the object?

• The object has a constant positive acceleration for the first five seconds, a constant negative velocity for the next five seconds, and a constant negative acceleration for the last five seconds.

• The object has a constant positive velocity for the first five seconds, is stopped for the next five seconds, and has a constant negative velocity for the last five seconds.

• The object has a constant positive acceleration for the first five seconds, is stopped the next five seconds, and has a constant negative acceleration for the last five seconds.

Answer explanation

On a position-vs-time graph, constant, positive velocity is shown by a straight line with a constant, positive slope. Constant negative velocity is shown by a straight line with a constant, negative slope. A straight horizontal line indicates no movement. Acceleration and deceleration are represented with curves. In the graph shown, the object has a constant positive velocity for the first five seconds, is stopped for the next five seconds, and has a constant negative velocity for the last five seconds.

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-1

A 1-kilogram bowling ball weighs about 10 Newtons on Earth. Which of the following correctly describes its weight and mass on Mars?

• weight on Mars < 10 Newtons; mass on Mars < 1 kilogram

• weight on Mars < 10 Newtons; mass on Mars = 1 kilogram

• weight on Mars < 10 Newtons; mass on Mars = 1 kilogram

Answer explanation

The weight of the bowling ball on Mars will be less than its Earth weight of 10 Newtons, but its mass on Mars will equal its 1 kilogram mass on Earth. Weight is a measure of how hard one mass pulls on another. The weight of the bowling ball is lower on Mars because Mars is less massive than Earth. Mass is a measure of the amount of matter in an object, so the mass of the ball does not change when the ball is moved to Mars.

Tags

NGSS.MS-PS2-4

Of the following, which is a statement of Newton's second law of motion?

• An object's acceleration depends on its mass and the net force acting on the object.

• An object's kinetic energy depends on its mass and speed.

• 
  The force of gravity between two objects depends on their masses and the distance between them.

• For every force on one object by a second, there is an equal and oppositely direct force on the second object by the first.

Answer explanation

Newton's second law can be expressed by F = ma, where F is the net force on the object, m is the object's mass, and a is the object's acceleration.

Tags

NGSS.MS-PS2-2

Which of the following is a valid reason for protecting the habitats of certain species, such as the Preble's meadow jumping mouse?

• to eliminate the negative effects of deforestation

• to prevent a reduction in biodiversity

• to prevent a decrease in the food supply of hawks

Answer explanation

One reason to protect endangered species is to protect biodiversity. A diverse gene pool prevents inbreeding and produces a balanced ecosystem.

Tags

NGSS.MS-LS2-4

NGSS.MS-LS2-5

Students are completing a lab in which they investigate the impact of soil pH on the growth rate of grass. This lab connects which two science disciplines?

• physics and space science

• physics and biology

• chemistry and biology

Answer explanation

This lab illustrates the interconnectedness between soil acidity (chemistry concept) and nutrient availability (biology concept).

Tags

NGSS.MS-LS2-4

NGSS.MS-LS1-5

NGSS.MS-LS2-1

Which of the following is measured by a barometer?

• atmospheric humidity

• atmospheric pressure

Which of the following is most commonly used to monitor the path of a hurricane on the open ocean?

• Weather balloons

• Satellite imagery

• Radar tracking

• Buoy data

What is a student most likely measuring if she is using a wind sock?

• Wind Speed

• Wind direction

Mild rain or snow followed by warmer temperatures often corresponds with which type of weather front?

• stationary

• occluded

• warm

Answer explanation

Warm fronts bring gentle precipitation and mild weather.

Tags

NGSS.MS-ESS2-5