1.
The tendency of an object to resist changes in its velocity is called:
Correct Answer
D. Inertia
Explanation
Inertia refers to the tendency of an object to resist changes in its velocity. It is a property of matter that causes an object to stay in its current state of motion, whether it is at rest or moving at a constant velocity. Inertia is related to the mass of an object, with greater mass resulting in greater inertia. This concept is described by Newton's first law of motion, which states that an object will remain at rest or continue moving in a straight line at a constant speed unless acted upon by an external force.
2.
A force that opposes motion, resulting from the contact of two surfaces is called:
Correct Answer
A. Friction
Explanation
Friction is the force that opposes motion when two surfaces come into contact. It acts in the opposite direction of the applied force and can be either static or kinetic. Static friction prevents an object from moving when a force is applied to it, while kinetic friction acts on moving objects. Inertia, on the other hand, is the tendency of an object to resist changes in its motion. Therefore, the correct answer is friction as it best describes the force that opposes motion resulting from the contact of two surfaces.
3.
Friction that opposes motion once the motion has already started is called:
Correct Answer
C. Kinetic Friction
Explanation
Kinetic friction is the correct answer because it refers to the friction that opposes motion once it has already started. It occurs when two surfaces are in contact and sliding past each other. Unlike static friction, which prevents the initial movement of an object, kinetic friction acts to resist the motion that is already occurring. This type of friction is dependent on factors such as the nature of the surfaces in contact and the normal force between them.
4.
Friction that opposes the initiation of motion is called:
Correct Answer
B. Static Friction
Explanation
Static friction is the correct answer because it refers to the frictional force that prevents an object from moving when a force is applied to it. It occurs when two surfaces are in contact but not moving relative to each other. Static friction is responsible for keeping objects at rest and opposes the initiation of motion.
5.
Which of Newton's 3 laws states: For every action, there is an equal and opposite reaction?
Correct Answer
C. Newton's Third Law
Explanation
Newton's Third Law states that for every action, there is an equal and opposite reaction. This means that whenever an object exerts a force on another object, the second object exerts a force of equal magnitude but in the opposite direction on the first object. This law explains how forces work in pairs and is fundamental in understanding the motion of objects.
6.
Which of Newton's 3 laws states: An object in motion (or at rest) will tend to stay in motion (or at rest) until it is acted upon by an outside force?
Correct Answer
A. Newton's First Law
Explanation
Newton's First Law, also known as the law of inertia, states that an object in motion will stay in motion and an object at rest will stay at rest unless acted upon by an external force. This law explains the concept of inertia, which is the tendency of an object to resist changes in its motion. In other words, if no force is applied to an object, it will maintain its current state of motion or rest.
7.
Which of Newton's 3 laws states: When an object is acted on by one or more outside forces, the total force is equal to the mass of the object times the resulting acceleration?
Correct Answer
B. Newton's Second Law
Explanation
Newton's Second Law states that when an object is acted on by one or more outside forces, the total force is equal to the mass of the object times the resulting acceleration. This law, also known as the law of acceleration, mathematically expresses the relationship between force, mass, and acceleration. It states that the force applied to an object is directly proportional to the mass of the object and the acceleration produced. In other words, the greater the force applied to an object, the greater its acceleration will be, and vice versa.
8.
A pilot is flying a mission to drop bombs on an enemy airfield. The plane is flying high and fast to the north, and the city is due north. Should the pilot drop the bombs before the plane is over the airfield, when the plane is over the airfield, or after the plane has passed the airfield?
Correct Answer
A. Before the plane reaches the airfield
Explanation
The pilot should drop the bombs before the plane reaches the airfield because the plane is flying high and fast to the north, and the city is due north. Therefore, dropping the bombs before reaching the airfield ensures that they will hit the intended target. Dropping them when the plane is directly over the airfield or after passing the airfield would result in the bombs missing the target.
9.
A cruel boy has placed a mouse on the outer edge of a disk. He slowly starts to spin the disk, accelerating it faster and faster until the disk and mouse are both spinning around at an alarming rate. What will happen to the mouse if the boy suddenly stops the disk without touching the mouse: will the mouse continue to spin like it was before; will the mouse stop with the disk; or will the mouse start moving straight, skidding off the disk?
Correct Answer
C. The mouse will start moving straight, skidding off the disk
Explanation
When the boy suddenly stops the disk, the mouse will continue to move in a straight line due to inertia. The mouse was initially spinning with the disk due to the force applied by the boy. However, when the disk stops abruptly, the mouse will not experience any force to keep it in circular motion. As a result, it will move in a straight line, skidding off the disk.
10.
An ice cube (mass = 1.0kg) slides down an inclined serving tray with an acceleration of 4.0 meters per second (squared). Ignoring friction, how much force is pulling the ice cube down the serving tray?
Please work your problem out on a separate sheet of paper for the answer.
Correct Answer
B. 4.0 Newtons down the tray
Explanation
The force pulling the ice cube down the serving tray can be calculated using Newton's second law, which states that force is equal to mass multiplied by acceleration. In this case, the mass of the ice cube is given as 1.0 kg and the acceleration is given as 4.0 meters per second squared. Therefore, the force pulling the ice cube down the serving tray is 1.0 kg multiplied by 4.0 meters per second squared, which equals 4.0 Newtons down the tray.
11.
A baseball player (mass = 75 kilograms) is running north towards a base. In order to avoid being tagged by the ball, the baseball player slides into the base. If his acceleration in the slide is 5.0 meters per second (squared) south, what is the kinetic frictional force between the baseball player and the ground?
Please work your problem out on a separate sheet of paper for the answer.
Correct Answer
D. 375 Newtons to the South
Explanation
The kinetic frictional force between the baseball player and the ground is 375 Newtons to the South. This can be determined using Newton's second law, which states that force is equal to mass multiplied by acceleration. The mass of the baseball player is given as 75 kilograms and the acceleration in the slide is 5.0 meters per second squared south. Therefore, the force can be calculated as 75 kg * 5.0 m/s^2 = 375 N. The negative sign indicates that the force is in the opposite direction of the player's motion, which is to the South.
12.
A man pushes a heavy cart. If the man exerts a force of 200 Newtons on the cart to keep it moving at a constant velocity, what is the frictional force between the cart and the ground? Is this kinetic friction or static friction?
Please work your problem out on a separate sheet of paper for the answer.
Correct Answer
D. The frictional force is 200 Newtons against the motion of the cart - Kinetic
Explanation
The frictional force between the cart and the ground is 200 Newtons against the motion of the cart. This is kinetic friction because the cart is moving at a constant velocity.
13.
You are looking through a physicist's laboratory notebook and notice two numbers for the friction between a block of wood and a laboratory bench. The numbers are 8 Newtons and 11 Newtons. Which one refers to static friction and which one refers to kinetic friction?
Correct Answer
A. 11 Newtons refers to static friction and 8 Newtons refers to kinetic friction
Explanation
The answer is 11 Newtons refers to static friction and 8 Newtons refers to kinetic friction. This is because static friction is the force that prevents an object from moving when a force is applied to it, and kinetic friction is the force that opposes the motion of an object when it is already moving. Since the block of wood is initially at rest on the laboratory bench, the friction force that prevents it from moving is the static friction force, which is 11 Newtons. Once the block starts moving, the friction force acting on it is the kinetic friction force, which is 8 Newtons.
14.
A woman pushes a box (mass = 30 kilograms). The static friction between the box and the ground is 20 Newtons, while the kinetic friction is 7 Newtons. How much force must the woman exert to get the box moving?
Please work your problem out on a separate sheet of paper for the answer.
Correct Answer
D. Greater than 20 Newtons
Explanation
The woman must exert a force greater than 20 Newtons to get the box moving. This is because the static friction between the box and the ground is 20 Newtons, which is the maximum force that can be applied before the box starts moving. Once the box starts moving, the force required decreases, and the kinetic friction is 7 Newtons. Therefore, the woman must exert a force greater than 20 Newtons to overcome the static friction and initiate the motion of the box.
15.
A woman pushes a box (mass = 30 kilograms). The static friction between the box and the ground is 20 Newtons, while the kinetic friction is 7 Newtons. With what force must she push the box in order to get it to accelerate at 1.0 meters per second (squared) to the west?
Please work your problem out on a separate sheet of paper for the answer.
Correct Answer
B. A force of 37 Newtons West
Explanation
The woman must apply a force greater than the static friction in order to overcome it and start the box's motion. Once the box is in motion, the force required to keep it moving at a constant velocity is equal to the kinetic friction. However, since the question asks for the force required to accelerate the box, the woman must apply a force greater than the kinetic friction. Therefore, the answer of 37 Newtons West is correct as it is greater than both the static and kinetic friction forces.
16.
When baseball players hit the ball hard enough, their bats can sometimes break. What is exerting a force on the bat, causing it to break?
Correct Answer
B. The ball
Explanation
When a baseball player hits the ball hard enough, the force of the player's swing is exerted on the bat. This force is transferred from the bat to the ball upon contact. If the force of the swing is too strong, it can exceed the structural integrity of the bat, causing it to break. Therefore, the force of the player's swing is the most likely explanation for the bat breaking when hit hard enough by the ball.