Forces — Chapter quiz · Physical Science: Matter, Forces & Energy, Grade 8

The initial net force is zero, consistent with the stated constant velocity. The later net force is 4 N right, causing acceleration to the right for the same cart. Zero net force permits steady motion rather than require rest; a force direction does not by itself give an instantaneous velocity.

The initial net force is zero, consistent with the stated constant velocity. The later net force is 4 N right, causing acceleration to the right for the same cart. Zero net force permits steady motion rather than require rest; a force direction does not by itself give an instantaneous velocity.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

Slowing is a change in velocity, so the zero-net-force claim needs revision. Identify interactions that can provide the nonzero net force.

Slowing is a change in velocity, so the zero-net-force claim needs revision. Identify interactions that can provide the nonzero net force.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

Net 9 N right; acceleration 9/3 = 3 m/s² right. Its initial leftward motion slows because acceleration opposes velocity.

Subtract opposing forces on the same receiver.

Compare acceleration direction with the supplied velocity.

Net 9 N right; acceleration 9/3 = 3 m/s² right. Its initial leftward motion slows because acceleration opposes velocity.

Response criteria

• Use the named labels, directions or supplied quantities accurately.
• Connect the visual evidence to the scientific mechanism or calculation.
• State the relevant model conditions or limitation.

The cart’s net force is 8−3=5 N rightward. The cart pushes the hand with 8 N leftward as the partner of the hand-on-cart interaction. The 3 N floor force belongs to another interaction. Net force on the cart and the pair force on the hand answer different questions.

The cart’s net force is 8−3=5 N rightward. The cart pushes the hand with 8 N leftward as the partner of the hand-on-cart interaction. The 3 N floor force belongs to another interaction. Net force on the cart and the pair force on the hand answer different questions.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

No. It can be slowing under a leftward net force or moving steadily with zero net force. Motion direction and net-force direction are different quantities.

No. It can be slowing under a leftward net force or moving steadily with zero net force. Motion direction and net-force direction are different quantities.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

Required net is 4×1.5 = 6 N right, leaving 4 N resistance left. The cart-on-hand partner belongs on the hand’s diagram, not the cart’s.

Use measured acceleration to find net force.

Keep the third-law partner on its separate receiver.

Required net is 4×1.5 = 6 N right, leaving 4 N resistance left. The cart-on-hand partner belongs on the hand’s diagram, not the cart’s.

Response criteria

• Use the named labels, directions or supplied quantities accurately.
• Connect the visual evidence to the scientific mechanism or calculation.
• State the relevant model conditions or limitation.

Mass remains 2 kg, while gravitational force depends on the local gravitational field. Weight equals mass × g, giving the supplied forces. To compare surface friction, match object load, contact procedure, travel direction and measurement, changing only the intended surface. Weight and friction are distinct forces, and air resistance can add another interaction.

Mass remains 2 kg, while gravitational force depends on the local gravitational field. Weight equals mass × g, giving the supplied forces. To compare surface friction, match object load, contact procedure, travel direction and measurement, changing only the intended surface. Weight and friction are distinct forces, and air resistance can add another interaction.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

At steady straight-line speed the net force is zero, so the pull balances resistance in the stated model. During acceleration the pull need not equal friction.

At steady straight-line speed the net force is zero, so the pull balances resistance in the stated model. During acceleration the pull need not equal friction.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

Use the illustrated study titled Gravity: masses, distance and free fall. Keep the observations, model and conditions separate.

The force rises from 8 to 16 relative units when one mass doubles at fixed separation, and falls to 2 when separation doubles at the reference masses. These model comparisons support attractive, mass- and distance-dependent interaction under the stated conditions. Feather/stone differences in air also involve drag and inertia; an ideal negligible-drag comparison does not depend on mass in the same way. Separate receivers for the interaction pair and name the model limit.

The force rises from 8 to 16 relative units when one mass doubles at fixed separation, and falls to 2 when separation doubles at the reference masses. These model comparisons support attractive, mass- and distance-dependent interaction under the stated conditions. Feather/stone differences in air also involve drag and inertia; an ideal negligible-drag comparison does not depend on mass in the same way. Separate receivers for the interaction pair and name the model limit.

Response criteria

• Compare one changed factor at a time.
• Explain attraction and appropriate force receivers.
• Distinguish gravity-only motion from significant drag.

Horizontal velocity 6 m/s; vertical velocity 0; vertical acceleration −10 m/s². Gravity continues acting downward.

Separate the two velocity components.

Distinguish zero vertical velocity from zero acceleration.

Response criteria

• State all three values with units.
• Keep gravity downward.
• Avoid claiming zero total velocity.

At the top after 0.8 s: horizontal velocity 3 m/s, vertical velocity 0, vertical acceleration −10 m/s². Total flight is 1.6 s, so range is 4.8 m under the same-height ideal model.

Vertical velocity loses 10 m/s each second, reaching zero after 0.8 s.

Symmetric ideal same-height return takes twice that time; multiply by horizontal speed.

At the top after 0.8 s: horizontal velocity 3 m/s, vertical velocity 0, vertical acceleration −10 m/s². Total flight is 1.6 s, so range is 4.8 m under the same-height ideal model.

Response criteria

• Use the named labels, directions or supplied quantities accurately.
• Connect the visual evidence to the scientific mechanism or calculation.
• State the relevant model conditions or limitation.

The objects affect one another without direct contact and remain coupled across the supplied paper barrier. The measured force decreases with separation in this range. These illustrative records do not establish a universal inverse-square rule for all magnet geometries or show that every barrier behaves like paper. A field is a model of the spatial influence, not a material stream of air.

The objects affect one another without direct contact and remain coupled across the supplied paper barrier. The measured force decreases with separation in this range. These illustrative records do not establish a universal inverse-square rule for all magnet geometries or show that every barrier behaves like paper. A field is a model of the spatial influence, not a material stream of air.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

Use the same source, test object, orientation, and measuring method. Change separation deliberately and repeat observations to check variation.

Use the same source, test object, orientation, and measuring method. Change separation deliberately and repeat observations to check variation.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

Use the illustrated study titled Field strength and stored energy. Keep the observations, model and conditions separate.

At fixed 0.2 A, changing turns from 10 to 20 raises the illustrative lift count 3→5; at fixed 20 turns, current 0.2→0.3 A changes it 5→7. These proxy outcomes support questions and a bounded trend, not a direct calibrated force law. Moving repelling magnets closer requires input work; separating attracting magnets can require input work instead. Energy is associated with the pair’s arrangement and can transfer into later motion.

At fixed 0.2 A, changing turns from 10 to 20 raises the illustrative lift count 3→5; at fixed 20 turns, current 0.2→0.3 A changes it 5→7. These proxy outcomes support questions and a bounded trend, not a direct calibrated force law. Moving repelling magnets closer requires input work; separating attracting magnets can require input work instead. Energy is associated with the pair’s arrangement and can transfer into later motion.

Response criteria

• Isolate turns/current using the proper records.
• Distinguish proxy measurement from force.
• Model potential energy, orientation and work.

Positive: upward. Negative: downward. Field direction uses the positive-test-charge convention.

Identify the definition of electric-field direction.

Reverse the force direction for a negative test charge.

Response criteria

• Name both directions.
• Explain the sign convention.
• Distinguish field from a path.

Outside N to S; inside S to N. Each cut piece has both N and S poles.

Trace a complete loop.

Identify both poles on each smaller magnet.

Response criteria

• Give both directions.
• Keep both poles on each piece.
• Distinguish magnetic poles from electric charge.

The negative charge feels force right, opposite the positive-test-charge convention. A neutral paper piece can polarize while keeping balanced total positive and negative charge.

Use the field convention before choosing the test-charge force.

Distinguish charge redistribution from transfer that changes net charge.

The negative charge feels force right, opposite the positive-test-charge convention. A neutral paper piece can polarize while keeping balanced total positive and negative charge.

Response criteria

• Use the named labels, directions or supplied quantities accurately.
• Connect the visual evidence to the scientific mechanism or calculation.
• State the relevant model conditions or limitation.

Using force = pressure × area, the piston forces are 20 N and 80 N. In an ideal hydraulic arrangement, the larger force acts through a smaller distance while displaced volumes balance, so energy is not created. The displaced-fluid model gives an 8 N buoyant force; floating equilibrium also requires the object’s weight to be balanced.

Using force = pressure × area, the piston forces are 20 N and 80 N. In an ideal hydraulic arrangement, the larger force acts through a smaller distance while displaced volumes balance, so energy is not created. The displaced-fluid model gives an 8 N buoyant force; floating equilibrium also requires the object’s weight to be balanced.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

Determine whether a string, floor, or other contact supplies a force. Rest alone does not establish that buoyancy and weight balance each other.

Determine whether a string, floor, or other contact supplies a force. Rest alone does not establish that buoyancy and weight balance each other.

Response criteria

• Use the supplied conditions and relevant evidence.
• Explain the scientific mechanism or calculation.
• State a meaningful limitation or testable next step.

The string supplies 3 N upward. Buoyancy alone is smaller than weight; the third force is needed to make the held object’s net force zero.

List all forces on the object.

Use 6+T−9 = 0 without calling the held state unsupported floating.

The string supplies 3 N upward. Buoyancy alone is smaller than weight; the third force is needed to make the held object’s net force zero.

Response criteria

• Use the named labels, directions or supplied quantities accurately.
• Connect the visual evidence to the scientific mechanism or calculation.
• State the relevant model conditions or limitation.