Question

Newton’s 1st law says that if something is not accelerating then it feels no net force. If the cart is sitting still it is certainly not accelerating. How can there be a reading on the force probe when the net force is zero? Explain.

Answer 1

Answer for this question is that force probe does not necesserily measures net force. What it mean is that there can be multiple set of forces acting on a body whose net resultant is zero(i.e. zero acceleration) but individually they may be non zero forces and force probe measures one of that. For real example a hanging mass, if connected to force probe will give value of its weight, which for sure is non zero, but the mass is not accelerating as the weight force is counter balaced by tension force.

One more possible situation is that a student may forget to set the probe to zero , which may give non-zero value as an error during measurement.

Let me know if it was helpful. Thank you!