A box sitting still on the ground by itself has a Normal Force of 700N, what is the mass? (gravity’s acceleration is 9.80 m/s²)

 71.43 kilograms

This value is approximate rounded to two decimal places.

Explanation:

The ground is pushing up with a normal force of 700 N. Because the box is sitting still, this means the force of gravity is pulling the box down with a force of 700N to keep things balanced.

If the force of gravity was greater than 700N, then the box would fall through the ground. If the force of gravity was smaller than 700N, then the box would be accelerated upward. Since neither event is happening, the force of gravity must be equal to the normal force.

Now turn to Newton's second law which says

F = ma

where F is the force, m is the mass and 'a' is the acceleration. We're given the acceleration of gravity is roughly 9.80 m/s^2. So a = 9.80

The force we'll plug in is F = 700. The value of m is unknown, but we can solve for it as such

F = ma

700 = m*9.80

700 = 9.08m

9.80m = 700

m = 700/9.80

m = 71.4285714285714

m = 71.43

The mass is roughly 71.43 kilograms.

a and c

c is 100% but i am confused in a

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000