Answer:
f = 4000 / 30 sec = 133.3 vibrations/sec
P = 1 / f = .0075 sec period of 1 vibration
D=rt
when biker A catches biker B, the time they've been riding is the same, so
t=t, or d/r=d/r
the rates are 6.4 and 4.7, so
d/6.4=d/4.7
biker B is 34m ahead, so
(d+34)/6.4=d/4.7
multiply both sides by 6.4*4.7:
4.7(d+34)=6.4d
4.7d+=6.4d+159.8
1.7d=159.8
d=94 meters
Another way to think of it is that biker A gains 1.7 meters on B every second (6.4-4.7=1.5), so the time it'll take for him to gain 34 meters is 34/1.7=20 seconds. In that time, biker B travels 4.7*20=94 meters
The purpose of the brush is supposed to be to lessen the amount of damage or wear placed upon the motor. I hope this helps with your answer choices since you did not post any.
Answer:
vb = 22.13 m/s
Explanation:
ma = 124 kg
mb = 13 kg
vi = 2.10 m/s
According to the property of conservation of momentum, and considering that, initially, both the astronaut and the bag moved together at 2.10 m/s:

The minimum final velocity of the bag, vb, the will keep the astronaut from drifting away forever occurs when va = 0:

The minimum final velocity of the bag is 22.13 m/s.