Forces Review

Write the mathematical relationship (Formulas) for the given variables.

Variables

Formula 1

Formula 2

Formula 3

Force (F), Mass (m), Acceleration (a)

F=mxa

M=f/a

A=f/m

Momentum (p), Mass (m), Velocity (V)

p=mxv

m=p/v

v=p/m

Identify the units for the variables

Variable

Units

Force (F)

N

Mass (m)

kg

Acceleration (a)

m/s

Velocity (V)

m/s2

Momentum (p)

kg⋅m/s)

Identify the two variables given in the question and solve for the third variable.

Use the correct units and show work.

Question

Variables

Show work

What net force is required to accelerate a car at a rate of 2 m/s if the car has a mass of 3,000 kg?

F=__6,000N____

m=_3,000 kg_____

a= 2 m/s______

What is the acceleration of softball if it has a mass of 0.5 kg and hits the catcher's glove with a force of 25 N?

F=___25N___

m=__0.5KG____

a= ____50m/s__

What is the momentum of a 10 kg ball traveling at a speed(v) of 5m/s?

p=___50kg⋅m/s___

m=__10kg____

V= 5m/s______

10x5= 50kg⋅m/s

What is the Velocity of a 10kg object with a momentum of 40 kg m/s?

p=__40 kg m/s____

m=_10kg_____

V= 4 m/s2______

40/10=4 m/s2

What is the mass of a box that weighs 200N on Earth?

F=_____200N_

m=20.39_kg_____

a= __1960m/s____

9.81x200n= 20.39

F = ma = (200 kg)(9.8 m/s/s) = 1960

What are Newton's Three Laws of Motion?

Name the Law, Explain it, and give one example.

Law

Explanation

Example

Newton's first law

states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia. The key point here is that if there is no net force acting on an object (if all the external forces cancel each other out) then the object will maintain a constant velocity. If that velocity is zero, then the object remains at rest. If an external force is applied, the velocity will change because of the force.

F = m * a

The second law

explains how the velocity of an object changes when it is subjected to an external force. The law defines a force to be equal to change in momentum (mass times velocity) per change in time. Newton also developed the calculus of mathematics, and the "changes" expressed in the second law are most accurately defined in differential forms. (Calculus can also be used to determine the velocity and location variations experienced by an object subjected to an external force.) For an object with a constant mass m, the second law states that the force F is the product of an object's mass and its acceleration a

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The third law

states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal force on object A. Notice that the forces are exerted on different objects. The third law can be used to explain the generation of lift by a wing and the production of thrust by a jet engine.

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