Question

question 1 (1 point) saved
listen
what is needed for work to be done on an object?
a force that causes motion
a force with no movement
a change in temperature
just touching the object
question 2 (1 point) saved
listen
work is only done when an object moves in the direction of the force.
true
false

Explanation:

• Question 1: According to the work - energy principle, work \(W = F\times d\times\cos\theta\) (where \(F\) is force, \(d\) is displacement, and \(\theta\) is the angle between force and displacement). If there is no motion (\(d = 0\)), \(W=0\). A change in temperature is related to heat transfer (thermodynamics) and not directly to mechanical work. Just touching an object without causing displacement does not do work. So, a force that causes motion (non - zero displacement) is needed for work to be done.
• Question 2: The formula for work \(W = F\times d\times\cos\theta\). When \(\theta = 0^{\circ}\) (object moves in the direction of the force, \(\cos\theta=1\)), \(W = F\times d\). But work can also be done when the object has a component of displacement in the direction of the force (e.g., when \(\theta = 30^{\circ}\), \(\cos\theta=\frac{\sqrt{3}}{2}\) and \(W=\frac{\sqrt{3}}{2}Fd\)). So, the statement "Work is only done when an object moves in the direction of the force" is too restrictive.

Answer:

• Question 1: A. A force that causes motion
• Question 2: False