Accepted Answer
applying one newton of force to an object of 1 kg accelerates it by 1 meter per secondmaisie applied .4 newtons to the block, so it should be accelerating at .4 m/sbut it actually accelerated at .25 m/s or .25 newtons reached the blockthe difference in force applied and force received is .15, which is the force of friction because that's how much force it stopped from reaching the blockforce of friction is .15 newtons