Motion and Forces

Suppose a bulldozer is being hauled at 50 km/h to a construction site on the back of a flatbed truck. From which reference point would the bulldozer not appear to be moving?

• the road
• a traffic light
• the truck driver
• a roadside tree

Carmen is helping load furniture and boxes onto a moving truck. She picks up boxes of her things, places them on a cart, and pushes the cart to the moving van. Which term best describes the type of force Carmen uses?

• contact
• friction
• gravity
• noncontact

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Ahmed saw all of these things as he walked to school this morning. Which one is an example of a force pushing downward toward the ground?

• A bird sat on a telephone wire.
• A woman moved her child from one place to another in a wagon.
• A man pulled weeds in his garden.
• A dog tugged on a rope a child held.

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Mr. Wang works in a recycling center. Recyclable materials arrive at the center mixed together. Workers use magnets to separate steel cans from other items. Which two statements are true about the force between a steel can and a magnet?

• Gravity pushes the can toward the magnet
• The force between the can and the magnet is a noncontact force.
• The attraction between the can and the magnet is a pull.
• The attraction between the can and the magnet is a push.

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Keisha has two large dogs and a small dog. The dogs like to play tug-the-rope together. Which statement correctly explains the amount and direction of the net force acting on the rope, and which direction the rope will move?

• The net force is 8 N to the left, and the rope will move to the right.
• The net force is 8 N to the left, and the rope will move to the left.
• The net force is 32 N to the left, and the rope will move to the left.
• The net force is 32 N to the right, and the rope will move to the right.

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Which of the following pictures shows the dogs exerting an unbalanced force on the rope? Check all that apply.

• 
• 
• 
• None of the pictures show an unbalanced force

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Daylon’s family just bought a new puppy, and Daylon decided to take him for a walk. He put the puppy in a wagon and pulled the wagon along the sidewalk. From which of these reference points does the puppy appear to be moving?

• Daylon
• the wagon
• the sidewalk
• the puppy's collar

Two school classes are playing tug-of-war with a rope. One class pulls on the rope with a 75 N force to the left, the other pulls with a 40 N force to the right. Which two statements describe this situation?

• The forces are balanced, and the rope does not move.
• The forces are unbalanced, and the rope will move to the left.
• The net force on the rope is 115 N to the right.
• The net force on the rope is 35 N to the left.

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You might have noticed that a feather falls slowly toward the ground, while a ball falls rapidly. Which statement correctly explains the motion of these objects?

• The ball does not experience fluid friction as it falls.
• Gravity is the only force acting on the feather and the ball.
• The acceleration of the ball and feather are the same.
• The feather experiences more fluid friction than the ball.

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Nicki rides her bike at a constant speed for 6 km. That part of her ride takes her 1 h. She then rides her bike at a constant speed for another 9 km. That part of her trip takes her 2 h. What is her average speed?

• 3.00 km/h
• 5.00 km/h
• 5.25 km/h
• 7.50 km/h