1.
A newton is equivalent to which of the following quantities?
Correct Answer
B. Kgâ€¢m/s^2
Explanation
A newton is equivalent to the quantity of kgâ€¢m/s^2. This is because a newton is the unit of force and is defined as the amount of force required to accelerate a mass of 1 kilogram at a rate of 1 meter per second squared. Therefore, the correct answer is kgâ€¢m/s^2.
2.
Which statement about the acceleration of an object is correct?
Correct Answer
A. The acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object.
Explanation
The correct answer is that the acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object. This means that if the net external force acting on an object increases, its acceleration will also increase. Conversely, if the mass of the object increases, its acceleration will decrease. This relationship is described by Newton's second law of motion, which states that the acceleration of an object is equal to the net force acting on it divided by its mass.
3.
A truck and a car uniformly accelerate from rest to a velocity of 3.0 m/s in equal time intervals. The truck is ten times as massive as the car. Which of the following statements is correct?
Correct Answer
A. The acceleration of the truck is 1/10 that of the car.
Explanation
In this scenario, both the truck and the car accelerate from rest to a velocity of 3.0 m/s in equal time intervals. However, the truck is ten times as massive as the car. According to Newton's second law of motion, force is directly proportional to mass and acceleration. Since the force applied to both the truck and the car is the same, but the mass of the truck is ten times greater than the car, the acceleration of the truck must be 1/10 that of the car. Therefore, the correct statement is that the acceleration of the truck is 1/10 that of the car.
4.
In which situation is the net force acting on a car zero?
Correct Answer
D. The car maintains both its speed and direction.
Explanation
When the net force acting on a car is zero, it means that the forces acting in opposite directions are balanced and cancel each other out. In this situation, the car will continue to move in the same direction with the same speed, without any change in its motion. This occurs when the forces pushing the car forward and the forces opposing its motion are equal in magnitude and opposite in direction, resulting in a net force of zero.
5.
Which are simultaneous equal but opposite forces resulting from the interaction of two objects?
Correct Answer
D. Action-reaction pairs
Explanation
Action-reaction pairs refer to the equal and opposite forces that occur when two objects interact with each other. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object exerts an equal and opposite force back on the first object. These action-reaction pairs are simultaneous and occur between the interacting objects. Therefore, action-reaction pairs are the correct answer to the question.
6.
Newton’s third law of motion involves the interactions of
Correct Answer
D. Two objects and two forces.
Explanation
Newton's third law of motion states that for every action, there is an equal and opposite reaction. This means that when two objects interact, they exert equal and opposite forces on each other. Therefore, the correct answer is "two objects and two forces."
7.
A hammer drives a nail into a piece of wood. Identify an action-reaction pair in this situation.
Correct Answer
C. The hammer exerts a force on the nail; the nail exerts a force on the hammer.
Explanation
The action-reaction pair in this situation is that the hammer exerts a force on the nail, and the nail exerts an equal and opposite force on the hammer. This is based on Newton's third law of motion, which states that for every action, there is an equal and opposite reaction.
8.
A batter strikes a baseball with a bat. Identify an action-reaction pair and describe the forces exerted by each.
Correct Answer
B. The batter exerts a force on the bat; the bat exerts a force on the batter.
Explanation
When a batter strikes a baseball with a bat, an action-reaction pair occurs. The batter exerts a force on the bat, causing it to accelerate and move towards the ball. Simultaneously, according to Newton's third law of motion, the bat exerts an equal and opposite force on the batter. This force can be felt as a recoil or vibration in the batter's hands. Therefore, the correct answer is "The batter exerts a force on the bat; the bat exerts a force on the batter."
9.
Two students reach for a jar of mustard at the same time. One student pulls to the left with a force of 13.2 N, while the other student pulls to the right with a force of 12.9 N. If the jar has a net acceleration of 0.44 m/s^{2} to the left, what is the mass of the jar?
Correct Answer
C. 0.68 kg
Explanation
The net force acting on the jar can be calculated by subtracting the force exerted to the right from the force exerted to the left. In this case, the net force is 13.2 N - 12.9 N = 0.3 N. According to Newton's second law of motion, the net force is equal to the mass of the object multiplied by its acceleration. Rearranging the formula, we can find the mass of the jar by dividing the net force by the acceleration. Therefore, the mass of the jar is 0.3 N / 0.44 m/s^2 = 0.68 kg.
10.
A certain cable of an elevator is designed to exert a force of 4.5 ´ 10^{4} N. If the maximum acceleration that a loaded car can withstand is 3.5 m/s^{2} (the current fastest elevators in the world undergo an acceleration of less than 3.2 m/s^{2}), what is the combined mass of the car and its contents?
Correct Answer
A. 12,857 kg
Explanation
The force exerted by the cable is equal to the mass of the car and its contents multiplied by the acceleration. Therefore, we can use the equation F = ma to solve for the mass. Rearranging the equation, we have m = F/a. Plugging in the given values, we get m = 4.5 x 10^4 N / 3.5 m/s^2 = 12,857 kg. Therefore, the combined mass of the car and its contents is 12,857 kg.