0 Km , Displacement is distance from starting point. Not distance of Journey.
When the projectile is at its maximum height above ground, it's at the point
of changing from rising to falling. At that exact point, its vertical speed is zero,
so the 14 m/s must be all horizontal velocity. That's not going to change.
Since we need to consider changes in vertical speed now, we need to make
some assumption about where this is all happening, so that we know the
acceleration of gravity. I'll assume that it's all happening on or near the Earth,
and the acceleration of gravity is 9.8 m/s².
I'm also going to neglect air resistance.
a). 1.2 sec before it reaches its maximum height, the projectile is rising
at a vertical speed of (1.2 x 9.8) = 11.76 m/s.
The magnitude of its velocity is
the square root of (14² + 11.76²) = 18.28 m/s, directed about 40° above horizontal.
b). 1.2 sec after it reaches its maximum height, the projectile is falling
at a vertical speed of (1.2 x 9.8) = 11.76 m/s.
The magnitude of its velocity is
the square root of (14² + 11.76²) = 18.28 m/s, directed about 40° below horizontal.
===========================
In 1.2 second before or after zero vertical speed, an object in free fall moves
(1/2) (g) (t²) = (4.9) (1.2²) = 7.06 meters .
c). & d).
1.2 seconds before it reaches maximum height, the projectile is located at
x = -14 m
y = -7.06 m
e). & f).
1.2 seconds after it reaches maximum height, the projectile is located at
x = +14 m
y = -7.06 m .
I hope you recognize that 6 answers, plus a little bit of explanation,
all for 5 points, ain't too shabby. You made out well.
Answer:
19.74 N
Explanation:
mass of ball (m) = 0.25 kg
radius (r) = 0.5 m
time (t) = 2 revolutions per seconds = 1/2 = 0.5 second per revolution
find the tension in the string
tension (T) = 
- where velocity (v) =
tension now becomes (T) = 
tension (T) = 
- now substituting the values of mass (m), time (t) and radius (r) into the equation above we have
tension (T) = 
tension (T) = 
= 
= 19.74 N
Answer:
2795.3 J
Explanation:
distance, d = 28 feet = 8.53 m
Force, F = 80 lb = 356 N
Angle, θ = 23°
Work = F x d x cos θ
W = 356 x 8.53 x cos 23
W = 2795.3 J
Thus, the work done is 2795.3 J.
Answer:
12.5 ft/s
Explanation:
Height of person = 6 ft
height of lamp post = 10 ft
According to the question,
dx / dt = 5 ft/s
Let the rate of tip of the shadow moves away is dy/dt.
According to the diagram
10 / y = 6 / (y - x)
10 y - 10 x = 6 y
y = 2.5 x
Differentiate both sides with respect to t.
dy / dt = 2.5 dx / dt
dy / dt = 2.5 (5) = 12.5 ft /s
