A student pulls on a rope attached to a box of books and moves the box down the hall. The student pulls with a force of 120 N at an angle of 30.0° above the horizontal. The box has a mass of 25.0 kg, and μk between the box and the floor is 0.27. Find the acceleration of the box

The answer is b hope this

Answer///(d) atoms contain small,negatively charged particles;

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.