Answer:
I believe the answer is B.)
Answer:1200 kg
Explanation:
Given
Electromagnet can lift a mass of 
Magnetic force necessary to hold mass is proportional to Magnetic field
and magnetic field (B) is proportional to NIA
where N=no of turns
I=current in the magnet
A=area of cross-section
When we double the no of turns and triple the current then
N becomes 2 N
I becomes 3 I
therefore magnetic field becomes 6 times
Thus magnetic force becomes 6 times and we can say that electromagnet can hold the 6 times of given weight
i.e. 
Answer:
Silica
Explanation:
The most commonly used abrasives are hydrated silica (softened silica), calcium carbonate (also known as chalk), and sodium bicarbonate (baking soda).
Answer:
F = 0.179 N
Explanation:
given,
length of the rod = 0.759 m
mass of the rod = 1.03 kg
force = ?
initial angular speed = 0 rad/s
final angular speed = 6.87 rad/s
time interval = 9.95 s
the angular acceleration



moment inertial of the rod

torque produced by the rod τ = I α
torque is also equal to τ = F L
now,
F L = I α


F = 0.179 N