You are pulling your little sister on her sled across an icy...

You are pulling your little sister on her sled across an icy (friction- less surface. When you exert a constant horizontal force of 120 $\mathrm{N}$ , the sled has acceleration of 2.5 $\mathrm{m} / \mathrm{s}^{2} .$ If the sled has a mass of 7.4 $\mathrm{kg}$ , what is the mass of your little sister?

You are pulling your little sister on her sled across an icy (friction-
less surface. When you exert a constant horizontal force of 120 $\mathrm{N}$ ,
the sled has acceleration of 2.5 $\mathrm{m} / \mathrm{s}^{2} .$ If the sled has a mass of 7.4 $\mathrm{kg}$ ,
what is the mass of your little sister?

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Key Concepts

Newton's Second Law of Motion

Newton's Second Law of Motion states that the net force acting on an object is equal to the mass of the object multiplied by its acceleration (F = m × a). This law is fundamental in analyzing how forces affect the motion of objects, and it provides a direct method for calculating the unknown mass when a net force and acceleration are known.

Frictionless Surface

A frictionless surface is an idealized concept where no frictional forces are present to oppose motion. The absence of friction simplifies the dynamics of a problem, as the only horizontal force acting is typically the applied force, allowing for straightforward application of Newton’s laws without complications from resistive forces.

System Approach in Dynamics

When dealing with multiple objects that move together, such as a sled and its rider, the system approach involves treating the combined objects as a single entity with a total mass equal to the sum of the individual masses. This approach uses the net force and overall acceleration to determine unknown quantities, simplifying the analysis of the dynamics involved.

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