In figure Car’s weight = 16,000 N. What is the external input force?

What is hidden during a lunar eclipse? isn't the moon hidden?

Wavelength,frequency,and energy are related.what happens to a wave as it’s wavelength gets shorter?

Assume you measured the mass of the cart to be (500 ± 1) g and the mass of the additional mass you put on the cart to be (500 ± 1) g as well. since the scale you are using in the lab cannot measure objects heavier than 600g you will have to sum up individual pieces and propagate the error. so what would be the mass and the standard error of the cart and the mass