What discovery did becquerel made by accident?

Ahowler monkey is the loudest land animal and, under some circumstances, can be heard up to a distance of 4.6 km. assume the acoustic output of a howler to be uniform in all directions and that the threshold of hearing is 1.0 × 10-12 w/m2. what is the acoustic power emitted by the howler

Atrain departs from its station at a constant acceleration of 5 m/s. what is the speed of the train at the end of 20s?

Sort the images based on whether there's a force of attraction or repulsion between the magnets shown. attraction repulsion