# 7 the answer is 4) because you need opposites in order to attract
# 8 I'm going to guess it is 4) because electricity is needed in order a light bolt to work.(don't take my word for this one I'm not sure but, the other answer are correct)
# 9 the answer is 4) because the comb dose collect negative charges from the hair in order to make the hair have positive charge.
Hope this helped : )
Answer:
To maintain enough time to prevent a collision, a system operating in air traffic where aircraft speed does not
fall below 100 km/h (most medium-sized UAVs and GA aircraft) will need to be able to detect obstacles which
subtend an arc-width of as small as 0.125 mra
Answer:
The force is 
Explanation:
The moment of Inertia I is mathematically evaluated as

Substituting
for M(Mass of the wheel) and
for
(Radius of wheel)


The torque on the wheel due to net force is mathematically represented as

Substituting 135 N for
(Force acting on sprocket),
for
(radius of the chain) and F is the force acting on the sprocket due to the chain which is unknown for now

This same torque due to the net force is the also the torque that is required to rotate the wheel to have an angular acceleration of
and this torque can also be represented mathematically as

Now equating the two equation for torque
Making F the subject

Substituting values


False, wood is a solid structure that is not see through