6. Intro to Forces (Dynamics)

An object at rest cannot remain at rest unless which of the following holds?

A $10‑\mathrm{lb}$ block A is moving downward with a speed of $6 \mathrm{ft}/s$ at a given instant. According to Newton's First Law, what can be concluded about the net force acting on the block at that instant if it continues to move downward at constant speed?

A $1-\mathrm{kg}$ ball is falling straight down and experiences an upward air resistance force of $2N$. What is the net force acting on the ball? (Assume acceleration due to gravity is $9.8m/s^2$.)

In a head-on collision between two cars of equal mass ($m$) moving at equal speeds ($v$) toward each other, what happens to the total momentum ($p$) of the system according to Newton's First and Second Laws?

A $5 \mathrm{kg}$ block is acted upon by two horizontal forces: $F_1=10 N$ to the right and $F_2=4 N$ to the left. What is the magnitude of the resultant force acting on the block?

In which of the following situations is the object experiencing unbalanced forces?

According to Newton's First and Second Laws, when lifting an object off the ground at constant velocity, what is the relationship between the upward force applied $F$ and the weight of the object $mg$?

According to Newton's First Law, what is the best explanation for why a large rock remains motionless on a flat sidewalk?

According to Newton's First and Second Laws, which of the following best describes the proper procedure to lift an object safely and efficiently?

A simply supported beam of length $4$ m is subjected to a uniformly distributed load of $4$ kN/m over its entire span. Let point A be the left support and point E be the right support. What are the reaction forces at supports A and E?

How does an airbag help protect a passenger in a car following a car accident according to Newton's First and Second Laws?

According to Newton's Second Law, what is the relationship between the net force $F$ acting on an object and its mass $m$ and acceleration $a$?

According to Newton's First and Second Laws, to determine a safe speed to travel around a curve of radius $r$ with a coefficient of static friction $\mu$ between the tires and the road, which of the following equations should be used?

A ball of mass $m$ moving with velocity $v$ strikes a wall and rebounds in the opposite direction with the same speed. If the contact time with the wall is ${\Delta }_t$, what is the magnitude $f$ of the average force exerted on the ball by the wall?

According to Newton's First and Second Laws, how can the motion of an object that is already moving be changed?