Force: แบบฝึกหัด

Which of the following is an example of a non-contact force?

Forces can be classified as contact forces or non-contact forces. Which of the following is an example of a contact force?

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?

Which of the following is an example of a non-contact force?

Which of the following units is used globally to represent the push or pull exerted on an object?

What is the name of the scientific instrument used to measure force, and what is the standard unit of force?

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.

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.

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>

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.