Hello there!
Plaque is a sticky substance made from leftover food particles and salvia that mix in your mouth.Not brushing plaque can cause some serious damage to your teeth as time flies, so it's important to brush your teeth 2-3 times a day.In the morning, afternoon, and nightime.Studies show not brushing your teeth at night can add on to the plaque thats already there causing cavities, bad breath, and some serious problems later on.
F = ma
1500 = 1500a
a = 1 m/s²
Average speed is the ratio of total distance moved by Chi in total time interval
So here we will have
Total distance = 100 m + 400 m
Total time taken = 5 min + 15 min = 20 min
now by the formula of average speed we know that
so average speed will be 1.5 km/h