C2 8.6C, 6.8A, 6.9C Newtons Law and Energy Transformation

When a coin is tossed in the air, it travels upward, gradually slows down, momentarily reaches zero speed, then moves back downward with increasing speed. Which statement best explains this change in the coin’s motion?

• The force of gravity causes the coin to change its velocity.

• The coin’s inertia decreases on the way up and increases on the way down.

• The action-reaction force pair of gravity and the applied force cancel each other.

• The coin remains in its state of upward motion until the force of friction acts upon it.

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-4

During a demonstration of Newton’s laws of motion, a student used the setup shown in Figure 1. The student flicked the index card with a fingertip, and the coin fell straight down into a plastic cup as shown in Figure 2. Which of these best explains why the coin fell straight down into the cup instead of remaining on the index card?

• The coin was at rest until the card was removed, so it tended to remain in the same location. Once the card was gone, the unbalanced force of gravity caused the coin to fall.

• Moving the card applied an action force on the coin. Since the card was gone, gravity applied a reaction force on the coin.

• The card had less mass than the coin, so a smaller force of gravity acted on the card. The larger force of gravity on the coin made it fall.

• The acceleration of the coin falling into the cup was equal and opposite to the acceleration of the card.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-4

When a skater pushes off a wall and skates backward before stopping, which statement best describes an action-reaction force pair?

• The wall exerts a force on the skater, and the skater exerts an equal and opposite force on the wall.

• The skater exerts a force on the wall, and the wall exerts a force on the skater in the same direction.

• The skater exerts a force on the wall, and the wall exerts a force on the skater in the opposite direction.

• The skater pushes off the wall, and the wall provides no reaction force.

Tags

NGSS.MS-PS2-1

During a lab investigation, students added four 50 g masses to two boxes and arranged the boxes so that they were motionless on a pulley, as shown in the diagram. The students then followed the procedure described in the box. The students recorded their observations after each procedure and reset the pulley system to the original conditions. During which procedures did students observe an unbalanced upward force on Box 1?

• Procedures 1, 2, and 3

• Procedures 4 and 5

• Procedures 3 and 4

• Procedures 1, 3, and 5

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NGSS.MS-PS2-2

NGSS.MS-PS2-5

A student jumps off a sled toward the west after it stops at the bottom of an icy hill. Based on the law of action-reaction, in what direction will the sled most likely move as the student jumps off?

• North

• South

• East

• West

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NGSS.MS-PS2-1

The picture shows an aerialist walking on a tightrope and holding a balancing bar. An action–reaction pair of forces exists between —

• the aerialist’s feet and the rope

• the rope and the balancing bar

• the two ends of the rope

• the aerialist’s arms and legs

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NGSS.MS-PS2-1

A teacher rubbed a match against a piece of sandpaper. The match started to burn. Which statement best describes the energy changes that occurred?

• The chemical energy stored in the match changed to thermal energy and light energy.

• The thermal energy stored in the match changed to light energy and chemical energy.

• The light energy and thermal energy stored in the match changed to mechanical energy.

• The light energy and thermal energy stored in the match changed to chemical energy.

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NGSS.MS-PS1-2

NGSS.MS-PS1-5

The blades of a wind turbine are at rest until the movement of air causes the blades to spin. Which energy transformation happens when the blades are spinning as shown?

• Electrical to mechanical

• Chemical to electrical

• Mechanical to electrical

• Chemical to mechanical

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NGSS.MS-PS3-1

NGSS.MS-PS3-5

Students build a circuit. The circuit has wires that connect a battery to a switch and a fan. Which energy transformations happen when the students close the circuit and the blades of the fan begin to spin?

• Chemical to mechanical to electrical

• Electrical to chemical to mechanical

• Chemical to electrical to mechanical

• Mechanical to electrical to chemical

In the classroom demonstration shown below, a rubber ball is dropped from Position 1. The ball bounces as shown. At which of these positions does the ball have both the greatest kinetic energy and the least potential energy?

• Position 1

• Position 2

• Position 3

• Position 4

Tags

NGSS.MS-PS3-1

NGSS.MS-PS3-2

NGSS.MS-PS3-5