Quais seriam os testes psicomotores adequados para crianças em fase de alfabetização?

Why there is no inductive reactance in dc circuits

The position of a crate sliding down a ramp is given by x=(0.05t^3) m, y=(1.7t^2) m, z=(6−0.85t^5/2) m, where t is in seconds. (a) determine the magnitude of the crate's velocity when t = 2 s. (b) determine the magnitude of the crate's acceleration when t = 2 s.

What do you think car designers do if the damage caused by a crash test is too severe?