Force, Motion, and Waves

An eighth-grade class is studying the motion of objects. They have learned the following concepts about motion. 

Motion occurs when there is a change in the position of an object with respect to a reference point.  

While the speed of the object may change at various times during a trip the average speed for the trip is found by dividing the total distance by the total time. 

The motion of the object can be changed by varying the amount of net force acting on the object or by varying the mass of the object.

 

The teacher asked students to design different investigations using the materials below to determine how mass and changing the forces acting on an object would change its motion.

 Materials:

1 - toy cart

3 - 10N masses

1 - pulley

1 - meter of string

 One group of students decided to design an investigation to determine how different amounts of mass on the toy cart would affect the speed of the toy cart.  They set up their investigation as shown below:

 The students hung the same mass shown as (M2) to pull the toy cart as it dropped and performed several trials using different masses in the toy cart (M1).

 Below is a table they made to record their results:

What step do the students need to include in their experimental design to best determine the effect of mass on the speed of the toy cart?

• Determine the total distance the toy cart traveled for each trial.

• Investigate how much force was used on the toy cart for each trial.

• Determine the effect of increasing the force pulling the toy cart.

• Investigate the time it takes a different toy cart to travel for each trial

Tags

NGSS.MS-PS2-2

An eighth-grade class is studying the motion of objects. They have learned the following concepts about motion. 

Motion occurs when there is a change in the position of an object with respect to a reference point.  

While the speed of the object may change at various times during a trip the average speed for the trip is found by dividing the total distance by the total time. 

The motion of the object can be changed by varying the amount of net force acting on the object or by varying the mass of the object.

 

The teacher asked students to design different investigations using the materials below to determine how mass and changing the forces acting on an object would change its motion.

 Materials:

1 - toy cart

3 - 10N masses

1 - pulley

1 - meter of string

 One group of students set up their investigation as shown below to determine how certain changes would affect velocity.  They hung the same amount of mass to pull the toy cart as it dropped shown as (M2). Then the students performed several trials using different masses in the toy cart (M1).

Which of the following is the best hypothesis for this investigation?

• If the mass of (M1) increases, then the toy cart will decrease in speed

• If the mass of (M1) decreases, then the toy cart will decrease in speed.

• If the net force on (M1) increases, then the toy cart will not change its speed.

• If the net force on (M1) decreases, then the toy cart will increase its speed.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

An eighth-grade class is studying the motion of objects. They have learned the following concepts about motion. 

Motion occurs when there is a change in the position of an object with respect to a reference point.  

While the speed of the object may change at various times during a trip the average speed for the trip is found by dividing the total distance by the total time. 

The motion of the object can be changed by varying the amount of net force acting on the object or by varying the mass of the object.

 

The teacher asked students to design different investigations using the materials below to determine how mass and changing the forces acting on an object would change its motion.

 Materials:

1 - toy cart

3 - 10N masses

1 - pulley

1 - meter of string

 One group of students set up their investigation as shown below to determine how certain changes would affect speed. The students performed several trials by pulling the toy cart (M1) with different masses shown as (M2).  The force of gravity pulls on (M2) to provide a force to move the cart.

Which of the following is the best hypothesis for this experimental design?

• If the mass of the toy cart increases then the toy cart will decrease in speed.

• If the mass of the toy cart decreases then the toy cart will decrease in speed

• If the net force on the toy cart increases then the toy cart will increase in speed.

• If the net force on the toy cart decreases then the toy cart will increase in speed. 

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

All the objects in the force diagrams shown below have the same mass.

 Which of the force diagrams would result in the greatest change in speed?

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Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

Mary designed an investigation to determine how changing the mass would affect the stopping distance of a cart. First, she rolled an empty cart and measured the distance it took the cart to stop. She added weight and rolled the cart again at the same speed and measured the distance again.  She then added a second weight and measured the distance needed to stop traveling at the same speed.

 Below are the results of her investigation.

Which of the following best explains the results of her investigation?

• More massive objects have more inertia, so it is harder to stop

• More massive objects have less inertia, so it is harder to stop.

• Less massive objects have more inertia, so it is harder to stop.

• Less massive objects have less inertia, so it is harder to stop.

Tags

NGSS.MS-PS2-2

William and his friends were asked to investigate how the mass of a toy car would impact its ability to stop. They rolled the same toy car with different masses down the ramp shown below. The students made sure that each toy car started at the same speed, but when they changed the mass of the toy car, the car's ability to stop would change.

Which of the graphs below best explains why the toy car's ability to stop changed?

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Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

 Which of the following best explains the force that moves the swimmer away from the wall?

• The reaction force of the wall pushing against her foot equally

• The action force of her foot pushing against the wall

• The reaction force of the wall pushing against her foot greater

• The action force of the wall pushing against her foot

Tags

NGSS.MS-PS2-1

A girl throws a ball up into the air. The picture shows how much the position of the ball changes every second.

What is the best explanation for how the position of the ball changes after each second?

• The force of gravity slows down the ball.

• The force of friction speeds up the ball

• The force from the girl's hand slows down the ball.

• The force of gravity speeds up the ball.

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-4

A scientist designed an investigation to measure the distance required to stop a car on several different road surfaces. The car was traveling at a speed of 10 m/s at the beginning of each trial. Below are the results of her investigation.

Which conclusion is best supported by the data from her investigation?

• The force of friction is the greatest on asphalt.

• The force of friction is the greatest on ice.

• The forward force from the engine was the greatest on asphalt.

• The forward force from the engine was the greatest on ice.

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

The graphs below represent different motions of a car.

Which graph represents the motion of a car moving at a constant speed?

• A

• B

• C

• D

Tags

NGSS.MS-PS3-1