5.2 Newton's first law  (Page 4/8)

Taking a frame attached to Earth as inertial, which of the following objects cannot have inertial frames attached to them, and which are inertial reference frames?

(a) A car moving at constant velocity

(b) A car that is accelerating

(c) An elevator in free fall

(d) A space capsule orbiting Earth

(e) An elevator descending uniformly

A woman was transporting an open box of cupcakes to a school party. The car in front of her stopped suddenly; she applied her brakes immediately. She was wearing her seat belt and suffered no physical harm (just a great deal of embarrassment), but the cupcakes flew into the dashboard and became “smushcakes.” Explain what happened.

Two forces of ${\overrightarrow{F}}_1=\frac{75.0}{\sqrt{2}}\left(\widehat{i}-\widehat{j}\right)\text{N}$ and ${\overrightarrow{F}}_2=\frac{150.0}{\sqrt{2}}\left(\widehat{i}-\widehat{j}\right)\text{N}$ act on an object. Find the third force ${\overrightarrow{F}}_3$ that is needed to balance the first two forces.

While sliding a couch across a floor, Andrea and Jennifer exert forces ${\overrightarrow{F}}_{\text{A}}$ and ${\overrightarrow{F}}_{\text{J}}$ on the couch. Andrea’s force is due north with a magnitude of 130.0 N and Jennifer’s force is $32\text{°}$ east of north with a magnitude of 180.0 N. (a) Find the net force in component form. (b) Find the magnitude and direction of the net force. (c) If Andrea and Jennifer’s housemates, David and Stephanie, disagree with the move and want to prevent its relocation, with what combined force ${\overrightarrow{F}}_{\text{DS}}$ should they push so that the couch does not move?