A skateboarder rolls off a 2.5 m high bridge into the river. If the skateboarder was originally moving at 7.0 m/s, how much time
1 answer:
Answer:
t = 0.714 s and x = 5.0 m
Explanation:
This is a projectile throwing exercise, in this case when the skater leaves the bridge he goes with horizontal speed
vₓ = 7.0 m / s
Let's find the time it takes to get to the river
y = y₀ + v_{oy} t - ½ g t²
the initial vertical speed is zero and when it reaches the river its height is zero
0 = y₀ + 0 - ½ g t²
t =
t = ra 2 2.5 / 9.8
t = 0.714 s
the distance traveled is
x = vₓ t
x = 7.0 0.714
x = 5.0 m
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Answer:
Velocity = 0.309 m/s
Along negative x axis
Explanation:
A pulse moving to the right along the x axis is represented by the wave function
y(x,t) = 2/ (x - 3t)² + 1
At t =0
y(x,0) = 2/ ((x - 3(0))² + 1)
=2 / (x² + 1)
At t = 1
y(x,t) = 2/ ((x - 3(1))² + 1)
= 2 /(( x - 3)² + 1)
At t = 2
y(x,t) = 2/ ((x - 3(2))² + 1)
= 2 /(( x - 6)² + 1)
For the pulse with expression y(x,t) = 4.5²
The Velocity is
V = 2.7 / 8.73
= 0.309 m/s
Answer:
Work out = 28.27 kJ/kg
Explanation:
For R-134a, from the saturated tables at 800 kPa, we get
= 171.82 kJ/kg
Therefore, at saturation pressure 140 kPa, saturation temperature is
= -18.77°C = 254.23 K
At saturation pressure 800 kPa, the saturation temperature is
= 31.31°C = 304.31 K
Now heat rejected will be same as enthalpy during vaporization since heat is rejected from saturated vapour state to saturated liquid state.
Thus, =
= 171.82 kJ/kg
We know COP of heat pump
COP =
=
= 6.076
Therefore, Work out put, W =
= 171.82 / 6.076
= 28.27 kJ/kg