Which of the following involves a non-zero net force?
I. A hockey-puck sliding at a constant speed on ice.
II. The earth revolving around the sun at a constant speed.
III. An object falling near the surface of the earth.
A) I only
B) III only
C) Both I and II
D) Both II and III
E) None of the above
Okay so I know that if there is a non-zero force, there has to be an acceleration. I put B, but I got it wrong. Please help me! Thanks in advance!
To determine which of the scenarios involve a non-zero net force, let's analyze each situation individually:
I. A hockey-puck sliding at a constant speed on ice.
If the puck is sliding at a constant speed on ice, it means that it is not accelerating. According to Newton's first law of motion, an object will continue moving at a constant velocity (which includes moving at a constant speed) unless acted upon by an external force. Since there is no acceleration or change in velocity, the net force acting on the hockey puck is zero. Therefore, option I does not involve a non-zero net force.
II. The earth revolving around the sun at a constant speed.
Similarly, if the Earth is revolving around the Sun at a constant speed, it means that it is not accelerating. However, in this scenario, the force of gravity from the Sun is the unbalanced force responsible for keeping the Earth in its orbit. Since the Earth is constantly changing its direction, it is continuously accelerating towards the Sun. Therefore, the net force acting on the Earth is non-zero. Therefore, option II involves a non-zero net force.
III. An object falling near the surface of the Earth.
When an object is falling near the surface of the Earth, it is subject to the force of gravity, which causes it to accelerate towards the center of the Earth. The acceleration due to gravity near the Earth's surface is approximately 9.8 m/s^2. As the object falls, its velocity increases, indicating that there is a non-zero net force acting on it. Therefore, option III involves a non-zero net force.
From the analysis, we can conclude that option D) Both II and III involve a non-zero net force.