Answer:
a)The direction the frictional force will acts is in the positive x direction.
Explanation:
a)The direction the frictional force will acts is in the positive x direction
b)in the horizontal direction, the total force F(total) is equal to 4times the frictional force in the wheel.
F(total)=4f
''f'' is taken as the frictional force.
c)4times the normal force on each wheel minus the acceleration equals zero i.e 4N(wheel)-a=0
=4N(wheel)-mg=0
d) torque is the force that tends to bend rotation
ζ=rf
but acceleration=4×frictional force
cross multiply
f=ζ/r
f=ma/4
ma/4=ζ/r
a=4ζ/r
I believe the answer is C. protoplanetary disc. Let me know if this helps
Answer:
The minimum magnetic field is 0.078 T.
Explanation:
Given that,
Current = 16 A
Side = 15 cm
Mass 
Mass each segment in given square loop is

We need to calculate the torque due to gravity
Using formula of torque


The torque due to magnetic field


The equilibrium condition

Put the value into the formula



Put the value into the formula


Hence, The minimum magnetic field is 0.078 T.
Answer:
1. Potential hazard
2. Mining opportunity
Explanation:
The two reason, why astronomers are so interested in the discovery of additional Earth-approaching asteroids:
1. Potential hazard: We have proof that the dinosaurs got extinct because of an asteroid/comet strike on Earth. Also we have seen the effects of the Tunguska event and Chelyabinsk tragedy. These are enough to show us that asteroids can be very dangerous and wipe out the life from Earth.
2. Mining Opportunity: We have discovered a lot of asteroids which contains a lot of metal and precious elements. There can be a possibility of mining such asteroids in the future and reducing the burden on Earth.