Unit 3 Retest 8th Grade Science

• The speed of the toy car increases due to forces greater than gravity.

• The speed of the toy car decreases due to balanced forces.

• The speed of the toy car increases due to unbalanced forces.

• 
  The speed of the toy car decreases due to friction.

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• The acceleration of the ball

• The velocity of the ball

• 
  The speed of the ball

• The velocity, speed, and acceleration all remained the same.

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Which of the following statements best describes how the speed and velocity of an object differ?

• Velocity specifies speed and direction, while speed has no specific direction.

• Velocity specifies speed, while speed includes a specific direction.

• Velocity specifies a change in speed over time, while speed specifies a change in distance over time.

• Velocity specifies a change in distance over time, while speed specifies a change in velocity over time.

• Shows the direction in which an object is traveling

• Shows how fast an object is traveling

• Shows a change in the speed of an object

• Shows the time it takes an object to travel a distance

• The vehicle was traveling at a constant speed.

• The vehicle was accelerating at a constant rate.

• 
  The speed of the vehicle was increasing.

• The acceleration of the vehicle was increasing.

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A roller coaster containing three cars is accelerating at 10 m/s² before it comes to an abrupt stop at the end of the ride. The mass of one car is 300 kg.

How much force was exerted on the roller coaster to bring it to a stop?

• 30 N

• 900 N

• 
  3000 N

• 9000 N

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A driver is transporting a watermelon in the back seat of a car traveling at a speed of 87 km per hour. The watermelon has a mass of approximately 3.5 kg. A deer standing in the roadway causes the driver to come to a sudden stop. The watermelon crashes into the back of the front seat with great force.

Which of Newton’s laws best explains why it is safer to wear your seatbelt and to tie down or buckle in any objects being transported in a vehicle?

• The law of force and acceleration

• The law of conservation of mass

• The law of action-reaction

• The law of inertia

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• A: The force of the bird on the wires.

  Re: The force of the fence post on the wires.

• A: The force of the wires on the wires.

  Re: The force of the wires on the fence post.

• A: The force of the wires on the fence post.

  Re: The force of the bird on the fence post.

• A: The force of the bird on the fence post.

  Re: The force of the fence post on the bird.

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