I thought that the formula for finding the net force of an object...?

Question

was mass times acceleration. The problem is:

An object near the surface of the earth with a weight of 100 N is accelerated at 4 m/s/s. What is the net force on the object?

My book says the answer is 40 N, but if the formula is mass times acceleration, shouldn't the answer be 400 N? Can somone clarify this for me? Thanks.

Answer 1

weight is not a mass, it is force. So you have to find the mass first.



weight = mg

100N = m(9.8)

m = 10.204kg



Fnet = ma

Fnet = (10.204kg) (4m/s^2)

Fnet = 40.816N



my answer is alittle bit off because i used 9.8ms^2 instead of 10m/s^2.



hope this helps.

Answer 2

Weight is different than mass. Weight is the force of gravity on an object. Accleration due to gravity is approximately 10m/s^2) The mass of the object is 100N/10m/s^2 or 10 kg. Then you can solve for the net force (10kg x 4m/s^2 = 40N)

Answer 3

Weight of 100N means that the gravitational force on the object is 100N meaning its mass is 10 kg (assuming the acceleration of gravity is 10 m/s/s).



Weight and mass are NOT the same thing.



F = m a = 10 kg * 4m/s/s = 40 N

Answer 4

I teach physics, and I've answered another question or two of yours tonight. Feel free to messenger me, I'm

fortitudinousskeptic

and I'll help you live. My messenger is running now.

The key to this problem is recognizing its weight, 100N. If gravity is roughly 10m/s/s, that would make its MASS 10kg using F=ma

Once you know its mass is 10kg, multiply that by the 4 m/s/s, and you get the 40N.

- kevin

Answer 5

Your object has a weight of 100 N.



What is its mass?