a force of 75 n at an angle of 15° to the direction of motion moves a chair 3 m. which change would result…

Answer:

D. decreasing the angle to 10°

Explanation:

Step1: Recall work - formula

The work formula is $W = Fd\cos\theta$, where $W$ is work, $F$ is force, $d$ is displacement, and $\theta$ is the angle between force and displacement.

Step2: Analyze option A

Original $F = 75$ N, new $F=60$ N. With $d$ and $\theta$ constant, since $W = Fd\cos\theta$, a decrease in $F$ will decrease $W$.

Step3: Analyze option B

Original $d = 3$ m, new $d = 2$ m. With $F$ and $\theta$ constant, since $W = Fd\cos\theta$, a decrease in $d$ will decrease $W$.

Step4: Analyze option C

Original $\theta=15^{\circ}$, new $\theta = 20^{\circ}$. The cosine function $y = \cos\theta$ is decreasing for $0^{\circ}\leq\theta\leq90^{\circ}$. So, $\cos(20^{\circ})<\cos(15^{\circ})$. With $F$ and $d$ constant, an increase in $\theta$ will decrease $W$.

Step5: Analyze option D

Original $\theta = 15^{\circ}$, new $\theta=10^{\circ}$. Since $\cos(10^{\circ})>\cos(15^{\circ})$ and with $F$ and $d$ constant, decreasing $\theta$ will increase $W$.