Please check my answers
A hammer is used to hit a nail into a board. Which statement is correct about the forces at play between the nail and the hammer?
The nail exerts a much smaller force on the hammer in the opposite direction.
The nail exerts a much smaller force on the hammer in the same direction.
The nail exerts an equal force on the hammer in the same direction.****
The nail exerts an equal force on the hammer in the opposite direction.
A person is being pulled by gravity with a force of 500 N. What is the force with which the person pulls Earth?
1,000 N
100 N
500 N****
250 N
A magnet pulls a piece of iron with a force of 1 N. What is the force that the iron piece exerts on the magnet?
The iron piece exerts a force of 1 N divided by the ratio of the weight of the iron piece to the weight of the magnet in the same direction.
The iron piece exerts a force of 1 N on the magnet in the same direction. ****
The iron piece exerts a force of 1 N on the magnet in the opposite direction.
The iron piece exerts a force of 1 N divided by the ratio of the weight of the iron piece to the weight of the magnet in the opposite direction.
Which statement is correct about the rotational inertia of a rotating object?
When mass moves closer to the point of rotation, rotational inertia decreases.
Rotational inertia is always decreasing because angular momentum is conserved.
When mass moves closer to the point of rotation, rotational inertia increases.
Rotational inertia is conserved because it is resistance to change in rotational motion. ****
A figure skater who is spinning suddenly opens up his arms. Which statement is correct about the rotation of the skater?
The skater spins slower because his rotational inertia has increased.
The skater spins faster because his rotational inertia has increased.****
The skater spins faster because his rotational inertia has decreased.
The skater spins slower because his rotational inertia has decreased.
answers are
1. "The nail exerts an equal force on the hammer in the opposite direction."
2. "500 N"
3. "The iron piece exerts a force of 1 N on the magnet in the opposite direction."
4. "When mass moves closer to the point of rotation, rotational inertia decreases."
5. "The skater spins slower because his rotational inertia has increased."
Newton 3 is about equal and opposite !
The nail exerts an equal force on the hammer in the opposite direction.
If I push the nail forward it pushes BACK on me,
Thank so much!
anna is 100% correct
The iron piece exerts a force of 1 N on the magnet in the opposite direction.
SAME PROBLEM
If the magnet pulls the iron up, the iron pulls the magnet down.
The skater spins slower because his rotational MOMENT OF INERTIA has increased.
Angular momentum is conserved.
L =angular momentum = I * omega = Moment of inertia * angular velocity
Moment of inertia = sum of all the masses times square of distances from rotation axis
When arms go out, Moment of inertia increases
so
omega must DECREASE to keep product, I * omega constant.
Besides, you know perfectly well that is the skater pulls her arms IN, she speeds up :)
To check your answers, we need to understand the concepts behind each question:
1. In the case of a hammer hitting a nail, the forces at play between the nail and the hammer are an action-reaction pair. According to Newton's third law of motion, for every action, there is an equal and opposite reaction. Therefore, the nail exerts an equal force on the hammer in the same direction. So, the correct answer is:
- The nail exerts an equal force on the hammer in the same direction.
2. When a person is pulled by gravity with a force of 500 N, according to Newton's third law, the person also exerts an equal and opposite force on the Earth. So, the correct answer is:
- The force with which the person pulls Earth is also 500 N.
3. Similar to the previous question, an action-reaction force pair is at play here. The magnet pulls the iron piece with a force of 1 N, and in response, the iron piece exerts an equal force on the magnet. So, the correct answer is:
- The iron piece exerts a force of 1 N on the magnet in the same direction.
4. Rotational inertia refers to an object's resistance to changes in rotational motion. According to the conservation of angular momentum, when an object's mass moves closer to the point of rotation, the rotational inertia decreases. So, the correct answer is:
- When mass moves closer to the point of rotation, rotational inertia decreases.
5. When a figure skater who is spinning suddenly opens up his arms, the moment of inertia increases. According to the conservation of angular momentum, when the moment of inertia increases, the rotational speed decreases. So, the correct answer is:
- The skater spins slower because his rotational inertia has increased.
Checking your answers based on these explanations:
- Question 1: You answered correctly.
- Question 2: You answered correctly.
- Question 3: You answered correctly.
- Question 4: You answered correctly.
- Question 5: You answered incorrectly. The correct answer is that the skater spins slower because his rotational inertia has increased.
You got 4 out of 5 correct answers. Well done!