問 1
1 点Which of the following is an example of a non-contact force?
Junior Secondary · Science
Force：練習問題
その場で採点される選択問題 5 問と、解説つきの記述問題 5 問。すべて「Force」からの出題です。
10 問26 点無料・登録不要
問 2
1 点Forces can be classified as contact forces or non-contact forces. Which of the following is an example of a contact force?
問 3
1 点A box of mass \(10 \text{ kg}\) is pulled horizontally across a rough surface by a constant applied force of \(35 \text{ N}\). If the kinetic friction force acting on the box is constant at \(15 \text{ N}\), what is the resultant (net) force acting on the box, and what is the resulting acceleration?
問 4
1 点Which of the following is an example of a non-contact force?
問 5
1 点Which of the following units is used globally to represent the push or pull exerted on an object?
問 6
2 点What is the name of the scientific instrument used to measure force, and what is the standard unit of force?
まず自分で答えを書いてから、解説と照らし合わせましょう。
問 7
3 点When a swimmer performs a breaststroke, they push the water backwards with their hands. Identify the reaction force and explain how it affects the swimmer's motion according to the law of action and reaction.
まず自分で答えを書いてから、解説と照らし合わせましょう。
問 8
6 点An engineer uses a machine to pull a heavy load across a rough road at a constant velocity. If the pulling force suddenly doubles, describe the immediate effect on the net force and the subsequent change in the load's motion, assuming the frictional force remains constant initially.
まず自分で答えを書いてから、解説と照らし合わせましょう。
問 9
4 点Friction is a force that opposes the relative motion between surfaces in contact.
(a)<\/b> A student finds it difficult to slide a heavy drawer open. Identify the resistive force<\/b> acting here and state whether it is a contact<\/b> or non-contact<\/b> force. (2 points)
(b)<\/b> Suggest two ways to reduce friction<\/b> in mechanical systems. (2 points)<\/p>
まず自分で答えを書いてから、解説と照らし合わせましょう。
問 10
6 点A worker is moving a heavy crate of mass \(50 \text{ kg}\) across a flat concrete floor. He initially pushes the crate with a constant horizontal force of \(200 \text{ N}\) to keep it moving at a steady speed.
(a) Identify the resistive force acting against the crate's motion and state its magnitude. Justify your answer using the concept of balanced forces. (2 points)
(b) To reduce the effort, the worker places ball bearings beneath the crate. Explain how this modification helps to reduce the friction experienced by the crate. (2 points)
(c) After adding the ball bearings, the friction is reduced to \(40 \text{ N}\). If the worker continues to push with \(200 \text{ N}\), calculate the net force acting on the crate and determine if the motion is uniform or non-uniform. (2 points)
まず自分で答えを書いてから、解説と照らし合わせましょう。
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