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# Physics question help Watch

1. 10. Each option gives a correct word equation involving force.Which option gives the definition of force?
A force = energy divided by displacement
B force = mass × acceleration
C force = pressure × area
D force = rate of change of momentum

Answer is D.
What exactly does the "definition" of force mean?
2. (Original post by Deathlotus)
10. Each option gives a correct word equation involving force.Which option gives the definition of force?
A force = energy divided by displacement
B force = mass × acceleration
C force = pressure × area
D force = rate of change of momentum

Answer is D.
What exactly does the "definition" of force mean?
It means the mathematical description from which all of the other equations are derived.
3. Think instead about electrical resistance. All of the following are true;

resistance = potenetial difference / current
resistance = resistivity * length / cross-sectional area
resistance = power disippated / current squared

But only one of these - the first one - is what we mean by resistance. This is the definition of resistance - the other equations just use this definition.

Of the four equations you give involving force, only one of them is the definition of force. I think that the problem here is that force is a term we use for a fair while in a "you know what I mean" way, before the definition is given - if the definition was given first, it would slow down the flow of most A Level courses, where you can do (for example) statics problems without having to worry about what a force actually is.

(The definition of force is wrapped up in Newton's second law.)
4. (Original post by Deathlotus)
10. Each option gives a correct word equation involving force.Which option gives the definition of force?
A force = energy divided by displacement
B force = mass × acceleration
C force = pressure × area
D force = rate of change of momentum

Answer is D.
What exactly does the "definition" of force mean?
Just as others have said, is the definition that other concepts of force are derived from it. It was Newton who introduced the concept of force, that is, the force was not a quantity that we could measure before Newton. He defined the force to be a quantity that would change the momentum of a body continuously. It is from this concept that mass x acceleration is derived.

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