The question asks to identify the condition under which an object's state of motion (rest or uniform motion) changes, according to Newton's first law. This law is also known as the law of inertia.
B) net external force
A net external force (also known as an unbalanced force) is the vector sum of all forces acting on an object. If this net force is non-zero, it will cause a change in the object's velocity (either speed or direction, or both), thus changing its state of rest or uniform motion. This directly aligns with Newton's first law.
The question asks to complete the statement of Newton's second law of motion. This law defines the relationship between force, mass, and acceleration. We need to recall the mathematical formulation of this law to identify the missing term.
B) mass — As derived from Newton's second law \( a = F_{\text{net}}/m \), acceleration is inversely proportional to the mass of the object.
The question asks to identify the type of force that friction represents when pushing a heavy box across the floor. We need to understand the definitions of different types of forces, particularly in the context of interaction between objects.
Correct Option: C) contact. Friction is a force that arises when two surfaces are in direct physical contact and one tries to slide over the other. Therefore, it is a contact force.
This problem can be solved by applying Newton's Second Law of Motion, which states that the net force acting on an object is equal to the product of its mass and acceleration (\(F = ma\)). We are given the mass of the object and the net force acting on it, and we need to find the acceleration.
The formula is:
\[ F = ma \]where \(F\) is the net force, \(m\) is the mass, and \(a\) is the acceleration.
Divide both sides by mass (\(m\)):
\[ a = \frac{F}{m} \]The unit for acceleration is meters per second squared (\(\text{m/s}^2\)).
Correct Option: A) 2 m/s²
Newton's first law of motion, also known as the law of inertia, states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. We need to identify the scenario where an object's state of motion changes due to an external force bringing it to rest or altering its motion from a constant velocity.
B) A soccer ball comes to rest after being kicked across the field. This scenario demonstrates that an object in motion will eventually come to rest if acted upon by external forces (like friction and air resistance). If these forces were absent, the ball would continue moving at a constant velocity, as per Newton's first law.
This question tests understanding of Newton's second law of motion, which describes the relationship between force, mass, and acceleration. We need to analyze how acceleration changes when the net force is doubled, assuming the mass remains constant.
where:
Substitute \(F_2 = 2F_1\) into the equation:
\[ a_2 = \frac{2F_1}{m} \]We know that \(a_1 = \frac{F_1}{m}\), so we can substitute \(a_1\) into the equation for \(a_2\):
\[ a_2 = 2 \left( \frac{F_1}{m} \right) \]\[ a_2 = 2a_1 \]A) The acceleration is doubled. This is correct because, according to Newton's second law (\(F=ma\)), acceleration is directly proportional to the net force when mass is constant. If \(F\) doubles, \(a\) must also double.