1.
For an action force, there must be a reaction force that
Correct Answer
D. Is exactly equal in magnitude
Explanation
The statement "for an action force, there must be a reaction force that is exactly equal in magnitude" is based on Newton's third law of motion. According to this law, every action has an equal and opposite reaction. This means that when one object exerts a force on another object, the second object exerts a force back on the first object that is equal in magnitude but opposite in direction. Therefore, the reaction force must be exactly equal in magnitude to the action force.
2.
An archer shoots an arrow. Consider the action force to be the bowstring against the arrow. The reaction to this force is the
Correct Answer
E. Arrow's push against the bowstring
Explanation
When an archer shoots an arrow, the action force is the bowstring pushing against the arrow. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the reaction to this force is the arrow's push against the bowstring. This means that as the bowstring pushes the arrow forward, the arrow pushes back against the bowstring with an equal force, propelling it forward.
3.
A player catches a ball. Consider the action force to be the impact of the ball against the player's glove. The reaction to this force is the
Correct Answer
B. Force the glove exerts on the ball
Explanation
When a player catches a ball, the impact of the ball against the player's glove is the action force. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the reaction force to the impact of the ball against the player's glove is the force that the glove exerts on the ball. This force allows the player to catch and hold onto the ball securely. The other options mentioned, such as the player's grip on the glove, friction of the ground against the player's shoes, and muscular effort in the player's arms, are not directly related to the reaction force in this scenario.
4.
A player hits a ball with a bat. The action force is the impact of the bat against the ball. The reaction to this force is the
Correct Answer
C. Force that the ball exerts on the bat
Explanation
When a player hits a ball with a bat, the action force is the impact of the bat against the ball. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the reaction to the action force of the bat hitting the ball is the force that the ball exerts on the bat.
5.
A baseball player bats a ball with a force of 1000 N. The reaction force that the ball exerts against the bat is
Correct Answer
C. 1000 N
Explanation
When a baseball player bats a ball with a force of 1000 N, the reaction force that the ball exerts against the bat is also 1000 N. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the force exerted by the ball on the bat is equal in magnitude but opposite in direction to the force exerted by the bat on the ball.
6.
As a ball falls, the action force is the pull of Earth on the ball. The reaction force is the
Correct Answer
C. Pull of the ball's mass on the Earth
Explanation
As the ball falls, the action force is the pull of Earth on the ball. This is due to the force of gravity, which attracts objects towards the center of the Earth. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the reaction force in this scenario is the pull of the ball's mass on the Earth. This means that while the Earth pulls the ball downwards, the ball also exerts an equal and opposite force on the Earth, although it may not be as noticeable due to the Earth's much larger mass.
7.
A person is attracted toward the center of Earth by a 500-N gravitational force. The Earth is attracted toward the person with a force of
Correct Answer
C. 500 N
Explanation
The Earth is attracted toward the person with a force of 500 N. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. In this case, the person is attracted towards the center of the Earth with a gravitational force of 500 N, and as a result, the Earth is attracted towards the person with an equal force of 500 N.
8.
A karate chop delivers a blow of 3000 N to a board that breaks. The force that acts on the hand during this event is
Correct Answer
C. 3000 N
Explanation
When a karate chop delivers a blow of 3000 N to a board that breaks, the force that acts on the hand during this event is 3000 N. This is because according to Newton's third law of motion, for every action, there is an equal and opposite reaction. So, the force exerted on the board (3000 N) is also exerted back on the hand, resulting in a force of 3000 N acting on the hand.
9.
Arnold Strongman and Suzie Small each pull very hard on opposite ends of a massless rope in a tug-of-war. The greater force on the rope is exerted by
Correct Answer
C. Both the same, interestingly enough
Explanation
In a tug-of-war, the force exerted on the rope by each participant is equal and opposite. This is due to Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. Therefore, the force exerted by Arnold on one end of the rope is balanced by the force exerted by Suzie on the other end. As a result, the forces are equal and the correct answer is "both the same, interestingly enough".
10.
Earth pulls on the moon. Similarly the moon pulls on Earth, evidence that
Correct Answer
A. These two pulls comprise an action-reaction pair
Explanation
The explanation for the given correct answer is that according to Newton's third law of motion, for every action, there is an equal and opposite reaction. In this case, Earth pulling on the moon and the moon pulling on Earth are two forces that are equal in magnitude but opposite in direction. This demonstrates an action-reaction pair, where the action is the pull of Earth on the moon and the reaction is the pull of the moon on Earth.
11.
The attraction of a person's body toward Earth is called weight. The reaction to this force is
Correct Answer
C. The person's body pulling on the Earth
Explanation
When a person's body is attracted towards the Earth, there is an equal and opposite reaction according to Newton's third law of motion. This means that the person's body exerts a force on the Earth, pulling it towards them. Therefore, the correct answer is "the person's body pulling on the Earth."
12.
A skydiver falls towards the Earth. The attraction of the Earth on the diver pulls the diver down. What is the reaction to this force?
Correct Answer
E. None of these
Explanation
The correct answer is none of these. The reaction to the force of the Earth's attraction on the skydiver is the skydiver exerting an equal and opposite force on the Earth, according to Newton's third law of motion. The options provided in the question, such as air resistance, water resistance, and attraction to other celestial bodies, do not represent the reaction force to the Earth's attraction on the skydiver.
13.
A automobile and a baby carriage traveling at the same speed collide head-on. The impact force is
Correct Answer
C. The same for both
Explanation
When two objects collide, the impact force depends on the mass and velocity of the objects involved. In this scenario, the automobile and the baby carriage are traveling at the same speed, which means they have the same velocity. However, the automobile has a much larger mass compared to the baby carriage. Since the impact force is directly proportional to mass and velocity, and the velocity is the same for both objects, the larger mass of the automobile will result in an equal but opposite force being exerted on both objects during the collision. Therefore, the impact force is the same for both the automobile and the baby carriage.
14.
A Mack truck and a Volkswagen traveling at the same speed have a head-on collision. The vehicle that undergoes the greatest change in velocity will be the
Correct Answer
A. Volkswagen
Explanation
The Volkswagen will undergo the greatest change in velocity because it has a smaller mass compared to the Mack truck. According to Newton's second law of motion, the force experienced by an object is directly proportional to its mass and acceleration. In a head-on collision, both vehicles experience the same force, but the smaller mass of the Volkswagen means that it will accelerate more compared to the larger and heavier Mack truck. Therefore, the Volkswagen will undergo a greater change in velocity.
15.
A car traveling at 100 km/hr strikes an unfortunate bug and splatters it. The force of impact is
Correct Answer
C. The same for both
Explanation
According to Newton's third law of motion, for every action, there is an equal and opposite reaction. When the car strikes the bug, the bug exerts a force on the car, and the car exerts an equal and opposite force on the bug. Therefore, the force of impact is the same for both the bug and the car.
16.
Your friend says that the heavyweight champion of the world cannot exert a force of 50 N on a piece of tissue paper with his best punch. The tissue paper is held in midair – no wall, no tricks. You
Correct Answer
A. Agree that it can't be done
Explanation
The tissue paper is very delicate and lightweight, while the heavyweight champion's punch is extremely powerful. The force exerted by the punch would be much greater than the delicate tissue paper can handle, causing it to tear or crumple. Therefore, it is highly unlikely that the heavyweight champion could exert a force of 50 N on the tissue paper without damaging it.
17.
A piece of rope is pulled by two people in a tug-of-war. Each pulls with 400 N of force. What is the tension in the rope?
Correct Answer
B. 400 N
Explanation
When two people are pulling on a rope in opposite directions with equal force, the tension in the rope is equal to the force applied by one person. In this case, each person is pulling with 400 N of force, so the tension in the rope is also 400 N.
18.
Two people, one twice as massive as the other, attempt a tug-of-war with 12 meters of massless rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of
Correct Answer
B. 4 m
Explanation
The heavier person slides a distance of 4 m. This can be explained by Newton's second law of motion, which states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. In a tug-of-war, the net force is determined by the difference in force applied by each person. Since the heavier person has twice the mass, they exert a greater force. As a result, the heavier person accelerates in the direction of the lighter person, sliding a greater distance before they meet.
19.
A bird sitting on the limb of a tree is moving about 30 km/s with respect to the sun. If the bird takes 1 second to drop down to a worm below, the worm would be 30 km downrange from the bird when it reached the ground. This faulty reasoning is best countered with Newton's
Correct Answer
A. First law
Explanation
The faulty reasoning in this scenario is assuming that the horizontal velocity of the bird (30 km/s) would affect the vertical distance the worm would be from the bird when it reaches the ground. However, according to Newton's first law of motion, an object in motion will continue moving with the same velocity unless acted upon by an external force. Therefore, the bird's horizontal velocity does not affect the vertical distance traveled by the worm.
20.
The force exerted on the tires of a car to directly accelerate it along a road is exerted by the
Correct Answer
D. Road
Explanation
The force exerted on the tires of a car to directly accelerate it along a road is exerted by the road itself. When the car's tires push against the road, the road pushes back with an equal and opposite force, known as the normal force. This normal force allows the tires to grip the road and propel the car forward. The engine provides the power to overcome friction and other resistive forces, but the force that directly accelerates the car comes from the road.
21.
A vehicle that weighs 4000 N on the surface of the Earth is travelling in outer space at a speed of 200 m/s. The smallest constant force that must be applied to stop it in 20 seconds is
Correct Answer
D. 4000 N
Explanation
In order to stop a vehicle, a force equal to its momentum change per unit of time needs to be applied. The momentum of the vehicle is given by the product of its mass and velocity. Since the mass of the vehicle is not provided, we cannot directly calculate the force. However, we know that weight is equal to mass times gravity. Therefore, the weight of the vehicle on Earth is equal to its mass times the acceleration due to gravity. Since the weight is given as 4000 N, we can assume that the mass of the vehicle is 400 kg. Using the formula for momentum, we can calculate the initial momentum of the vehicle. Dividing this momentum by the given time of 20 seconds, we find that a force of 200 N is required to stop the vehicle. Therefore, the correct answer is 4000 N.
22.
A vehicle that weights 400 N on the surface of the Earth is traveling in outer space at a speed of 400 m/s . It can be stopped by applying a constant force of 20 N for
Correct Answer
E. 800 seconds
Explanation
In outer space, where there is no friction or resistance, an object will continue to move at a constant velocity unless acted upon by an external force. The force required to stop the vehicle can be found using Newton's second law, which states that force is equal to mass times acceleration. Since the vehicle's mass is not given, it can be assumed to be constant. The acceleration required to stop the vehicle can be found using the equation acceleration = change in velocity / time. In this case, the change in velocity is 400 m/s (the initial velocity) and the time is 800 seconds. Therefore, the force required to stop the vehicle is 400 m/s divided by 800 seconds, which equals 0.5 N. Since the force required to stop the vehicle is 20 N, it will take 800 seconds to stop the vehicle by applying a constant force of 20 N.