12-Newton's law os Motion. The net force acting on a box is 18 newtons upward. The box accelerates at a rate of 3 m/s 2.

Transcription

1 Read each question carefully. 1) The net force acting on a box is 18 newtons upward. The box accelerates at a rate of 3 m/s 2. What is the box's mass? 6 kg 15 kg 21 kg 54 kg 2) A motorcycle and a van collide into each other while traveling the same speed. Upon impact, the motorcycle flies away from the van before crashing to the ground, while the van barely moves in comparison. What best describes how the forces the two vehicles exert on each other compare? The force the motorcycle exerts on the van is greater. The force the van exerts on the motorcycle is slightly greater. The force the van exerts on the motorcycle is much greater. The forces the vehicles exert on each other are equal and opposite. 1

2 3) A moth flies into a car's windshield as the car is traveling down the highway. The car exerts a force of 81,000 newtons eastward on the moth. What best describes the force the moth exerts on the car? The moth exerts a force of less than 1 newton westward on the car. The moth exerts a force between 1 and 81,000 newtons westward on the car. The moth exerts a force of exactly 81,000 newtons westward on the car. The moth exerts a force of more than 81,000 newtons westward on the car. 4) Which of the following is the best example of Newton's third law? A bicycle remains motionless until a force is applied. A jet moves forward as it thrusts air backward. A heavy car accelerates more slowly than a lightweight car. A ball remains in motion because it has inertia. 2

3 5) Which of the following best describes Newton's first law? If there are external unbalanced forces acting upon an object, the object will remain motionless. The force of attraction between two objects is dependent upon the objects' masses and the distance between them. If all the external forces acting on an object cancel each other out, the object will remain in its state of motion. If one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object. 6) A car pushes downward on the ground as the ground pushes upward on the car. Which of Newton's laws does this example best illustrate? law of acceleration law of inertia third law of motion second law of motion 3

4 7) In what circumstance would an object maintain a constant velocity? when the object has no inertia when the object experiences no friction when there is no net force acting on the object when the forces acting on an object remain constant 8) The net force on a 4-kilogram book is 50 newtons downward. At what rate is the book accelerating? 12.5 m/s 2 downward 46 m/s 2 downward 54 m/s 2 downward 200 m/s 2 downward 4

5 9) Which of the following is the best example of Newton's first law? A car moves at a constant velocity until its brakes increase the force of friction acting on it. As a person bumps into a wall, the force the wall exerts on them is equal to the force they exert on the wall. A baseball will continue to increase in speed unless acted upon by an external force. As the distance between two objects decreases, the force of gravity between them increases. 10) Which of the following best describes Newton's first law? Objects resist changes to their states of motion. For every action, there is an equal and opposite reaction. Inertia is the relationship between the various forces acting on an object. An object's acceleration depends on its mass and the net force acting on it. 5

6 11) According to Newton's first law, in what circumstance would an object's velocity most likely increase? when an additional force acts on the object when all of the forces acting on the object are balanced when the mass of the object is proportional to the forces acting on it when the force of gravity acting on the object is equal to the force of friction 12) The net force on a 60-kilogram cyclist is 180 newtons southward. At what rate is the cyclist accelerating? 3 m/s 2 southward 120 m/s 2 southward 240 m/s 2 southward 10,800 m/s 2 southward 6

7 13) A girl kicks a ball eastward with a force of 8 newtons. The ball's mass is 0.4 kilograms. At what rate is the ball accelerating? 3.2 m/s 2 eastward 5 m/s 2 eastward 20 m/s 2 eastward 32 m/s 2 eastward 14) A ball is accelerating at a rate of 8 m/s 2. The net force acting upon the ball is 20 newtons downward. What is the ball's mass? 2.5 kg 12 kg 28 kg 160 kg 7

8 15) A 22-kilogram wagon is accelerating at a rate of 2 m/s 2 westward. What is the net force acting upon the wagon? 0.09 newtons west 11 newtons west 20 newtons west 44 newtons west 16) A boy jumped off of his skateboard, and the skateboard rolled backwards. What best explains why the skateboard rolled backwards? because the force the boy exerted on the skateboard caused the skateboard to decrease in speed because the force the boy exerted on the skateboard was opposite in direction of the force the skateboard exerted on the boy because the force the boy exerted on the skateboard caused the skateboard to push down against the ground because the force the boy exerted on the skateboard was opposite in direction of the force the ground exerted against the skateboard 8

9 17) An airfoil is deflected upward as the airflow is deflected downward. Which of Newton's laws does this example best illustrate? universal law of gravitation first law of motion second law of motion third law of motion 18) A 50-kilogram skateboarder travels north, accelerating at a rate of 2 m/s 2. What is the net force acting upon the skateboarder? 25 newtons northward 48 newtons northward 52 newtons northward 100 newtons northward 9

10 19) Which of the following best describes Newton's first law? The acceleration of an object is inversely proportional to the mass of the object. If there is no net force acting upon an object, the object will remain in its state of motion. If a person exerts a force on an object, the object exerts an equal and opposite force on the person. The net force acting on an object is dependent upon the object's mass and its acceleration. 20) In what circumstance would an object remain at rest? when there is only one force acting on it when the forces acting on it remain balanced when the object's momentum remains very low when there is no friction acting on it 10

11 21) The net force acting on a platform is 375 newtons upward. The platform accelerates at a rate of 3 m/s 2. What is the platform's mass? 62 kg 75 kg 125 kg 1125 kg 22) Which of the following is the best example of Newton's first law? A planet's orbit is dependent upon its mass and distance from the sun. A soccer ball remains motionless on the ground until it is kicked. When two cars collide, they exert equal and opposite forces on each other. A falling rock's acceleration is dependent upon gravity and wind resistance. 11

12 23) A person leans against a wall, and the wall exerts an equal and opposite force on the person. Which of Newton's laws does this example best illustrate? third law of motion law of inertia second law of motion law of universal gravitation 24) Which of the following best describes Newton's third law? All objects remain in their state of motion until they are acted upon by an external force. An object's acceleration is dependent upon its mass and the net force acting upon it. If object A exerts a force on object B, then object B exerts an equal and opposite force on object A. Objects in a vacuum will share the same acceleration regardless of their masses. 12

13 25) A girl is pulling a wagon that holds her baby brother. Which statement is true? The wagon is pulling on the girl with the same force that she is pulling on it. The force her baby brother exerts on the wagon is greater than the force the wagon exerts on him. The girl is able to make the wagon move because she is pulling harder on the wagon than the wagon is pulling on her. The force the girl exerts on the wagon is equal to the force the wagon exerts against the ground. 26) Which of the following best describes Newton's third law? Objects need to be pushed in order to accelerate. When you push an object, the object pushes back. The push force on an object must be unbalanced. Friction resists the push force on objects. 13