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3 years ago

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A boat leaves a dock at 7:00 pm and travels due south at a speed of 20 km/h. another boat has been heading due east at 15 km/h a

nd reaches the same dock at 8:00 pm. how many minutes after 7:00 pm were the two boats closest together? (round your answer to the nearest minute.)

1 answer:

xxMikexx [17]3 years ago

7 0

Zero minute
Because the traveling boat is faster .
And this is my answer

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1.a bag is dropped from a hovering helicopter. the bag has fallen for 2 s. what is the ball's velocity at the instant its hittin

omeli [17]

1. The bag's velocity immediately before hitting the ground.

Recall this kinematics equation:

Vf = Vi + aΔt

Vf is the final velocity, Vi is the initial velocity, a is the acceleration, and Δt is the time elapsed.

Given values:

Vi = 0m/s (you assume this because the bag is dropped, so it falls starting from rest)

a is 9.81m/s² (this is the near-constant acceleration of objects near the surface of the earth)

Δt = 2s

Plug in the values and solve for Vf:

Vf = 0 + 9.81×2

Vf = 19.62m/s

2. The height of the helicopter.

Recall this other kinematics equation:

d = ViΔt + 0.5aΔt²

d is the distance traveled by the object, Vi is the initial velocity, a is the acceleration, and Δt is the time elapsed.

Given values:

Vi = 0m/s (bag is dropped starting from rest)

a = 9.81m/s² (acceleration due to gravity of the earth)

Δt = 2s

Plug in the values and solve for d:

d = 0×2 + 0.5×9.81×2²

d = 19.62m

3. Time of the bag's fall and its velocity immediately before hitting the ground... if it started falling at 2m/s

Reuse the equation from question 2:

d = ViΔt + 0.5aΔt²

Given values:

d = 19.6m (height of the helicopter obtained from question 2)

Vi = 2m/s

a = 9.81m/s² (acceleration due to earth's gravity)

Plug in the values and solve for Δt:

19.6 = 2Δt + 0.5×9.81Δt²

4.91Δt² + 2Δt - 19.6 = 0

Use the quadratic formula to get values of Δt (a quick Google search will give you the formula and how to use it to solve for unknown values):

Δt = 1.8s, Δt = −2.2s

The formula gives us 2 possible answers for Δt but within the situation of our problem, only the positive value makes sense. Reject the negative value.

Δt = 1.8s

Now we can use this new value of Δt to get the velocity before hitting the ground:

Vf = Vi + aΔt

Given values:

Vi = 2m/s

a = 9.81m/s²

Δt = 1.8s (result from previous question)

Plug in the values and solve for Vf:

Vf = 2 + 9.81×1.8

Vf = 19.66m/s

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How does the interstellar medium affect our view of most of the galaxy?

Vsevolod [243]

Answer: It prevents us from seeing most of the galactic disk with visible and ultraviolet light.

(hope this helps) :)

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3 years ago

The velocity - time graph of a ball of mass 25g moving on road is as given below:

lana [24]

Assume that the ball rolls to the right.

From the velocity-time graph, the acceleration is
a = (0 - 10 m/s)/(4 - 0 s) = -2.5 m/²

Part (a)
Because the mass of the ball is 25g or 0.025 kg, the force that the road exerts on the ball is
F = (0.025 kg)*(-2.5 m/s²) = -0.0625 N
The force is negative because it acts in opposition to the motion of the ball.

Answer: 0.0625 N to the left.

Part (b)
The direction of the force exerted by the road is to the left because it opposes the motion of the ball to the right.

Part (c)
The unit force is 1 N (Newton), with the dimension (kg-m)/s².

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The theory of the plate tectonics uses the convection cells in the upper mantle layer as the foundation for the movement of the continents.
To put it simple the process is explained like the convection cells create a lot of pressure, that pressure, supported by the high temperatures and magma, influence the crust above, and manage to crack it on certain places. As the crust cracks, it becomes a separate entity, and under the enormous force from bellow it slowly moves into a particular direction, and that is actually the movement of the tectonic plates.

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A box on a ramp is connected by a rope to a winch. The winch is turned so that the box moves down the ramp at a constant speed.

Marrrta [24]

Answer:

Option B:

The normal force

Explanation:

The normal force does no work as the box slides down the ramp.

Work can only be done when the force succeeds in moving the object in the direction of the force.

All the other forces involved have a component that is moving the box in their direction.

However, the normal force does not, as it points downwards into the ramp. Since the normal force is pointing into the ramp, and the box is sliding down the ramp, we can say that no work is being done by the normal force because the box is not moving in its direction (which would have been the box moving into the ramp)

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