Hệ số ma sát µ = 0,2; Khối lượng m = 4 kg;
Lực F = 12 N;
Góc  = 30 độ
Lấy g = 10 m/s2
Hợp lực tác dụng vào vật có độ lớn bằng bao nhiêu?

The temperature in gavin's oven is a sinusoidal function of time. gavin sets his oven so that it has a maximum temperature of 280°f and a minimum temperature of 240°. once the temperature hits 280°, it takes 20 minutes before it is 280° again. gavin's cake needs to be in the oven for 30 minutes at temperatures at or above 270°. he puts the cake into the oven when it is at 260° and rising. how long will gavin need to leave the cake in the oven? (round your answer to the nearest minute.)