1.
A fan was set on a table next to a stack of cards. The fan was turned on to low and then to high, blowing some of the cards off the table. Which of these statements is the best example of Newton's First law of motion in this situation?
Correct Answer
A. The cards are acted upon by an unbalanced forceÂ
Explanation
According to Newton's First Law of Motion, an object at rest will stay at rest and an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force. In this situation, the cards were initially at rest on the table. When the fan was turned on, it created an unbalanced force that caused the cards to move and eventually fall off the table. Therefore, the statement "The cards are acted upon by an unbalanced force" is the best example of Newton's First Law of Motion in this situation.
2.
A basketball, soccer ball, and a football were kicked. Which of these statements is the best example of Newton's First law of motion in this situation?
Correct Answer
B. Each ball rolled to a stop due to the unbalanced force of friction.
Explanation
According to Newton's First Law of Motion, an object will remain at rest or continue to move in a straight line at a constant velocity unless acted upon by an external force. In this situation, each ball rolled to a stop, indicating that an unbalanced force (friction) acted upon them to bring them to a halt. This aligns with Newton's First Law as it demonstrates that an external force is required to change the motion of an object.
3.
The driver of a taxi stops suddenly and all of the loose objects in the cab fly forward. According to Newton’s 1st Law of Motion, why did this happen?
Correct Answer
A. Since the objects were loose, they continued moving until acted upon by a net force.
Explanation
According to Newton's 1st Law of Motion, an object at rest will stay at rest and an object in motion will stay in motion with the same speed and in the same direction unless acted upon by an external force. In this case, the loose objects in the cab were already in motion due to the movement of the taxi. When the driver suddenly stopped the taxi, the objects continued moving forward due to their inertia until they were acted upon by a net force, which in this case was the sudden stop of the taxi.
4.
A balloon powered rocket is shown here. When the air in the balloon is released, the rocket will move forward. What is the reason the rocket moves forward?
Correct Answer
D. The escaping air creates a net force pushing the rocket forward.
Explanation
The correct answer is that the escaping air creates a net force pushing the rocket forward. When the air is released from the balloon, it creates a force in the opposite direction, pushing the rocket forward according to Newton's third law of motion. This force propels the rocket forward, causing it to move.
5.
The driver of a taxi stops to pick up a large family with many pieces of heavy luggage. Based on Newton's Second law of motion, the driver should expect that the taxi will
Correct Answer
D. take longer to both accelerate and stop
Explanation
According to Newton's Second Law of Motion, the acceleration of an object is directly proportional to the net force applied to it and inversely proportional to its mass. In this scenario, the taxi is carrying a large family with heavy luggage, which increases the mass of the taxi. As a result, the net force required to accelerate or decelerate the taxi will be greater, leading to a longer time taken to both accelerate and stop. Therefore, the correct answer is that the taxi will take longer to both accelerate and stop.
6.
After learning about Newton's Second law, a student decides that a parachute reduces the force a person feels when landing by reducing —
Correct Answer
C. A person's acceleration
Explanation
A parachute reduces the force a person feels when landing by reducing their acceleration. According to Newton's Second Law, force is directly proportional to mass and acceleration. When a person with a parachute lands, the parachute creates air resistance, which slows down the person's acceleration. As a result, the force experienced by the person upon landing is reduced. Therefore, the correct answer is a person's acceleration.
7.
A baseball, softball, and a tennis ball were all thrown with the same force. Which of these statements is the best example of Newton's 2nd Law of Motion in this situation?
Correct Answer
C. The softball accelerated the most because it has the greatest mass.
8.
A boy on ice skates is standing in the middle of an ice rink. He throws a football in the direction shown in the picture. What will be the direction of the boy's motion after he throw the ball? Remember the 3rd Law of Motion (Law of Action and Reaction).
Correct Answer
B. To the left
Explanation
According to the 3rd Law of Motion, for every action, there is an equal and opposite reaction. When the boy throws the football to the right, there will be a reaction force pushing him to the left. Therefore, the direction of the boy's motion after he throws the ball will be to the left.
9.
Two skaters are standing in the middle of an ice skating rink. Skater 1 has a mass of 50kg and Skater 2 has a mass of 45 kg. When they push off from one another, Skater 1 has a speed of 2 m/s. What must be the speed of Skater 2?
Hint: Momentum of Skater 1 divided by mass of Skater 2.
Correct Answer
A. 2.2 m/s
Explanation
The momentum of Skater 1 is given by the product of their mass (50 kg) and their speed (2 m/s), which is 100 kg*m/s. To find the speed of Skater 2, we divide this momentum by their mass (45 kg). Therefore, the speed of Skater 2 must be 2.2 m/s.
10.
A 500 kg cannon shoots a 10 kg cannonball with a velocity of 100 m/s. What is the recoil velocity of the cannon?
Hint: Momentum of the cannonball divided by mass of the cannon
Correct Answer
A. 2 m/s
Explanation
The recoil velocity of the cannon can be determined using the principle of conservation of momentum. According to this principle, the total momentum before the cannonball is fired is equal to the total momentum after the cannonball is fired. The momentum of an object is calculated by multiplying its mass by its velocity. In this case, the momentum of the cannonball is (10 kg)(100 m/s) = 1000 kg*m/s. Since the mass of the cannon is 500 kg, the recoil velocity can be calculated by dividing the momentum of the cannonball by the mass of the cannon: 1000 kg*m/s / 500 kg = 2 m/s. Therefore, the correct answer is 2 m/s.
11.
What is the difference between velocity and speed?
Correct Answer
A. Velocity has magnitude and direction; speed has magnitude only.
Explanation
Velocity and speed are both terms used to describe the rate at which an object moves. However, they differ in one key aspect. Velocity is a vector quantity, meaning it has both magnitude (numerical value) and direction. On the other hand, speed is a scalar quantity, which means it only has magnitude. In simpler terms, velocity not only tells us how fast an object is moving but also in which direction it is moving, while speed only tells us how fast the object is moving without any information about its direction.
12.
Which of the following has the greatest momentum?
Correct Answer
B. 500 kg car traveling at 16 m/s
Explanation
The momentum of an object is calculated by multiplying its mass by its velocity. In this case, the car has the greatest momentum because it has the highest mass (500 kg) and velocity (16 m/s). The ball, truck, and child all have lower masses and velocities, resulting in lower momentum values.
13.
A 10 N force is applied to a 6 kg box. Assume the floor is frictionless, Determine the acceleration of the box.
Correct Answer
C. One point seven meter per second square
Explanation
The acceleration of an object can be calculated using Newton's second law of motion, which states that the acceleration of an object is directly proportional to the net force applied to it and inversely proportional to its mass. In this case, a 10 N force is applied to a 6 kg box. Using the formula F = ma, we can rearrange it to solve for acceleration (a = F/m). Plugging in the values, we get a = 10 N / 6 kg = 1.7 m/s^2. Therefore, the acceleration of the box is 1.7 meter per second square.
14.
A person kicks a 4 kg door with a 48 N force causing the door to accelerate at 12 m/s^{2} . What is the magnitude of the force exerted by the door on the person?
Correct Answer
A. 48 Newtons
Explanation
The magnitude of the force exerted by the door on the person is 48 Newtons because of Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. When the person kicks the door with a force of 48 N, the door exerts an equal force of 48 N back on the person.
15.
The weight of an object on Earth is determined by
Correct Answer
A. Multiplying the mass of the object in kilogram with acceleration due to gravity of planet Earth which is equivalent to nine point eight meters per second square.
Explanation
The weight of an object on Earth is determined by multiplying the mass of the object in kilograms with the acceleration due to gravity of planet Earth, which is equivalent to nine point eight meters per second square. This is because weight is a measure of the force exerted on an object due to gravity, and the acceleration due to gravity on Earth is approximately 9.8 m/s^2. The greater the mass of an object, the greater the force of gravity acting on it, resulting in a greater weight.