A force of \(7 \mathrm{~N}\), making an angle \(\theta\) with the horizontal, acting on an object displaces it by \(0.5 \mathrm{~m}\) along the horizontal direction. If the object gains K.E. of \(2 \mathrm{~J}\), what is the horizontal component of the force? (A) \(2 \mathrm{~N}\) (B) \(4 \mathrm{~N}\) (C) \(1 \mathrm{~N}\) (D) \(14 \mathrm{~N}\)

Short Answer

Expert verified
(B) \(4 \mathrm{~N}\)

Step by step solution

01

Recall the work-energy theorem

The work-energy theorem states that the work done on an object is equal to the change in the object's kinetic energy: \[W = \Delta KE\]
02

Calculate the work done

Since the object gains a kinetic energy of 2 J, the work done by the force on the object is also 2 J: \[W = 2 \mathrm{~J}\]
03

Recall the formula for work done

The work done by a force on an object is given by: \[W = Fd \cos{\theta}\] Where \(F\) is the magnitude of the force, \(d\) is the displacement, and \(\theta\) is the angle between the force and displacement.
04

Substitute the known values

We know that the total force has a magnitude of 7 N, the displacement is 0.5 m, and the work done is 2 J. Let's substitute these values into the formula: \[2 \mathrm{~J} = (7 \mathrm{~N})(0.5 \mathrm{~m}) \cos{\theta}\]
05

Calculate the horizontal component of the force

The horizontal component of the force is given by: \[F_x = F \cos{\theta}\] Since we want to find the horizontal component of the force, we need to calculate \(F_x\) from the equation above. First, let's rewrite the equation to find \(\cos{\theta}\): \[\cos{\theta} = \frac{2 \mathrm{~J}}{(7 \mathrm{~N})(0.5 \mathrm{~m})}\] Now, substitute this into the formula for the horizontal component of the force: \[F_x = (7 \mathrm{~N})\left(\frac{2 \mathrm{~J}}{(7 \mathrm{~N})(0.5 \mathrm{~m})}\right)\] Now simplify this expression: \[F_x = 4 \mathrm{~N}\] So the horizontal component of the force is 4 N. The correct answer is (B) \(4 \mathrm{~N}\).

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