20. a 900-n paratrooper is falling from a fighter plane with her parachute open. if the air resistance is equal to 700-n, what can you tell about her motion? *hint: draw the free body diagram before answering*
a. the paratrooper will speed up moving downward.
b. the paratrooper will stop and hover in midair.
c. the paratrooper will slow down moving downward.
d. the paratrooper will fall at a constant velocity.
21. what direction does the force of friction act in relation to the motion of a sliding object?
a. the same direction
b. the opposite direction
c. it depends on the mass of the sliding object
22. which is the correct free-body diagram for a rightward-moving skateboarder slowing to a stop?
a.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\end{tikzpicture}
b.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw- (1.5,0.5) -- (2.5,0.5) noderight {$f_{app}$};
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw- (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
c.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw- (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
d.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw- (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
23. which is the correct free-body diagram for an egg falling from a nest? **ignore air resistance.
a.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\end{tikzpicture}
b.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw- (1.5,0.5) -- (2.5,0.5) noderight {$f_{app}$};
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw- (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
c.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw- (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
d.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw- (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw- (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw- (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
24. four objects are shown with their mass and velocity. which one of the following objects has the smallest inertia?
\begin{tikzpicture}
\
odedraw at (0,0) {a \
10 kg \
$v = 0$ m/s};
\
odedraw at (2,0) {b \
2 kg \
$v = 5$ m/s};
\
odedraw at (4,0) {c \
5 kg \
$v = 5$ m/s};
\
odedraw at (6,0) {d \
5 kg \
$v = 1$ m/s};
\end{tikzpicture}
25. what happens to the acceleration of an object if the net force acting on it is increased from 5 n to 10 n? note: its mass remains constant. the acceleration...
a. decreases.
b. increases.
c. is 0.
26. on your way to school one day, the car in front of you comes to a sudden stop and you have to stop really quickly. which of the following safety devices would be most helpful in this situation?
a. seat belt - your body is moving forward due to inertia.
b. crumple zone - to absorb the force of the crash.
c. rear - view mirror - you need to check behind you.
d. headrest - your head flies backwards due to inertia.
27. newtons 3rd law of motion states:
a. all collisions lose energy
b. the acceleration is the same if the mass is the same
c. all collisions gain energy
d. for every action, theres an equal and opposite reaction

Question

20. a 900-n paratrooper is falling from a fighter plane with her parachute open. if the air resistance is equal to 700-n, what can you tell about her motion? *hint: draw the free body diagram before answering*
 a. the paratrooper will speed up moving downward.
 b. the paratrooper will stop and hover in midair.
 c. the paratrooper will slow down moving downward.
 d. the paratrooper will fall at a constant velocity.
21. what direction does the force of friction act in relation to the motion of a sliding object?
 a. the same direction
 b. the opposite direction
 c. it depends on the mass of the sliding object
22. which is the correct free-body diagram for a rightward-moving skateboarder slowing to a stop?
 a.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\end{tikzpicture}
 b.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw-> (1.5,0.5) -- (2.5,0.5) noderight {$f_{app}$};
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw-> (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
 c.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw-> (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
 d.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw-> (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
23. which is the correct free-body diagram for an egg falling from a nest? **ignore air resistance.
 a.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\end{tikzpicture}
 b.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw-> (1.5,0.5) -- (2.5,0.5) noderight {$f_{app}$};
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw-> (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
 c.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw-> (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
 d.
\begin{tikzpicture}
\draw (0,0) rectangle (1,1);
\draw-> (-0.5,0.5) -- (-1.5,0.5) nodeleft {$f_{frict}$};
\draw-> (0.5,-0.5) -- (0.5,-1.5) nodebelow {$f_{grav}$};
\draw-> (0.5,1.5) -- (0.5,2.5) nodeabove {$f_{norm}$};
\end{tikzpicture}
24. four objects are shown with their mass and velocity. which one of the following objects has the smallest inertia?
\begin{tikzpicture}
\
odedraw at (0,0) {a \
 10 kg \
 $v = 0$ m/s};
\
odedraw at (2,0) {b \
 2 kg \
 $v = 5$ m/s};
\
odedraw at (4,0) {c \
 5 kg \
 $v = 5$ m/s};
\
odedraw at (6,0) {d \
 5 kg \
 $v = 1$ m/s};
\end{tikzpicture}
25. what happens to the acceleration of an object if the net force acting on it is increased from 5 n to 10 n? note: its mass remains constant. the acceleration...
 a. decreases.
 b. increases.
 c. is 0.
26. on your way to school one day, the car in front of you comes to a sudden stop and you have to stop really quickly. which of the following safety devices would be most helpful in this situation?
 a. seat belt - your body is moving forward due to inertia.
 b. crumple zone - to absorb the force of the crash.
 c. rear - view mirror - you need to check behind you.
 d. headrest - your head flies backwards due to inertia.
27. newtons 3rd law of motion states:
 a. all collisions lose energy
 b. the acceleration is the same if the mass is the same
 c. all collisions gain energy
 d. for every action, theres an equal and opposite reaction

Accepted Answer

### Question 20
# Brief Explanations:
The paratrooper's weight (force due to gravity) is 900 N downward, and air resistance is 700 N upward. Net force $ F_{net}=900 - 700 = 200\space N $ downward. A net force means acceleration in the direction of the net force (downward), so she speeds up downward. Option a is wrong (she speeds up, not slow down), b is wrong (no hovering), d is wrong (constant velocity needs net force zero).
# Answer: c. The paratrooper will speed up moving downward.

### Question 21
# Brief Explanations:
Friction opposes the relative motion of a sliding object. If an object slides, friction acts opposite to its direction of motion. So it's the opposite direction of the object's motion.
# Answer: b. The opposite direction

### Question 22
# Brief Explanations:
A rightward - moving skateboarder slowing to a stop: There is gravity ($ F_{grav} $) downward, normal force ($ F_{norm} $) upward (balanced), and friction ($ F_{frict} $) leftward (opposing motion, causing slowing). Option a has no friction, b has an applied force (not present), c has no friction. Option d has $ F_{norm} $ up, $ F_{grav} $ down, $ F_{frict} $ left.
# Answer: d (the diagram with $ F_{norm} $ up, $ F_{grav} $ down, $ F_{frict} $ left)

### Question 23
# Brief Explanations:
Ignoring air resistance, an egg falling from a nest has only gravity ($ F_{grav} $) acting downward (no normal force or friction as it's in free - fall, not in contact with a surface, and air resistance is ignored). Option a shows only $ F_{grav} $ downward. Option b has friction and applied force (not present), c has normal force (not present), d has friction and normal force (not present).
# Answer: a (the diagram with only $ F_{grav} $ downward)

### Question 24
# Brief Explanations:
Inertia is directly proportional to mass ($ I\propto m $). The object with the smallest mass has the smallest inertia. Among 10 kg, 2 kg, 5 kg, 5 kg, the 2 kg object (object b) has the smallest mass.
# Answer: b (the 2 - kg object)

### Question 25
# Brief Explanations:
From Newton's second law $ F = ma $, so $ a=\frac{F}{m} $. If mass $ m $ is constant and net force $ F $ increases from 5 N to 10 N, then $ a=\frac{10}{m} $ is greater than $ a=\frac{5}{m} $. So acceleration increases.
# Answer: b. increases.

### Question 26
# Brief Explanations:
When the car stops suddenly, your body moves forward due to inertia. A seat belt restrains your body from moving forward, preventing injury. Crumble zone absorbs force of crash (not for restraining body), rear - view mirror is for checking behind, headrest is for when head flies backward (not forward motion here).
# Answer: a. seat belt - your body is moving forward due to inertia.

### Question 27
# Brief Explanations:
Newton's 3rd law states that for every action, there is an equal and opposite reaction. Option a: collisions can be elastic (no energy loss) or inelastic, so wrong. Option b: relates to Newton's 2nd law ($ F = ma $), wrong. Option c: collisions can lose or gain energy (inelastic vs elastic), wrong.
# Answer: d. for every action, there's an equal and opposite reaction

Sovi.AI - AI Math Tutor

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Explanation:

Question 20

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Question 21