Mike drives his car 60 km in 55 minutes. What is the average speed?
1 answer:
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Answer:
a.14 s
b.70 s
Explanation:
a.Let the sidewalk moving in positive x- direction.
Speed of sidewalk relative to ground=
Speed of women relative to sidewalk=v=1.5m/s
The speed of women relative to the ground
Distance=35 m
Time=
Using the formula
Time taken by women to reach the opposite end if she walks in the same direction the sidewalk is moving=
b.If she gets on at the end opposite the end in part (a)
Then, we take displacement negative.
Speed of sidewalk relative to ground=
Speed of women relative to sidewalk=v=-1.5 m/s
The speed of women relative to the ground=
Time=
Hence, the women takes 70 s to reach the opposite end if she walks in the opposite direction the sidewalk is moving.
Answer:
The speed at which the ball rolled off the end of the table is 3.3 m/s
Explanation:
Hi there!
Please, see the attached figure for a graphical description of the problem. Notice that the origin of the frame of reference is located at the edge of the table.
The position vector of the ball can be calculated as follows:
r = (x0 + v0x · t, y0 + v0y · t + 1/2 · g · t²)
Where:
r = position vector.
x0 = initial horizontal position.
v0x = initial horizontal velocity.
t = time.
y0 = initial vertical position.
v0y = initial vertical velocity.
g = acceleration due to gravity.
When the ball reaches the ground, its position will be:
r final = (3, -4)
Then:
3 = x0 + v0x · t
-4 = y0 + v0y · t + 1/2 · g · t²
Since the origin of the frame of reference is located at the edge of the table, x0 and y0 = 0. v0y is also 0 ( see the initial velocity vector in the figure to elucidate why). Then:
3 m = v0x · t
-4 m = 1/2 · g · t²
We can solve for "t" in the equation of the y-component and use it in the equation of the x-component to obtain v0x:
-4 m = 1/2 · g · t²
-4 m = -1/2 · 9.8 m/s² · t²
8 m / 9.8 m/s² = t²
t = 0.9 s
Then:
3 m = v0x · 0.9s
3 m/ 0.9 s = v0x
v0x = 3.3 m/s
The speed at which the ball roll off the end of the table is 3.3 m/s
