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ruslelena [56]
4 years ago
5

A boat takes 4.0 h to travel 36 km down a river, then 5.0 h to return.how fast is the river flowing

Physics
1 answer:
dem82 [27]4 years ago
5 0
<span>Let us refer to boat speed as X and water speed as Y On the way down the stream, the water speed is added to the speed of the boat: speed of the boat (X) + water speed (Y) is 9km/h When the boat is moving upstream, water speed is taken away from the speed of the boat: Speed of the boat (X) - water speed (Y) is 7.2 km/h Therefore: X + Y = 9 : X - Y = 7.2 2X = 16.2 X = 8.1 X + Y = 9 8.1 + Y = 9 Y = 0.9 The river is flowing at 0.9 km/h</span>
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Mary is driving a car of mass 900 kilograms toward the north with a velocity of
lorasvet [3.4K]
Since both cars move together after the collision, then this is an example of an inelastic collision. The formula for an inelastic collision is as follows:

m1u1 + m2u2 = (m1 + m2)v

Where:

m1 = mass of the first object
m2 = mass of the second object
u1 = initial velocity of the first object
u2 = initial velocity of the second object
v = final velocity

Substituting the given values to solve for v:

900*22 + 900*15 = (900 + 900)v
v = 18.5 m/s
3 0
4 years ago
Read 2 more answers
What is the electric force acting between two charges of 0.0042 C and −0.0050 C that are 0.0030 m apart?
Black_prince [1.1K]

Answer:

A.−2.1 × 10^10 N

Explanation:

Using the formula;

E = k Q1Q2/d²

Where;

E is the electrical force  

k is the constant  

Q1, Q2 are the two charges  and

d is the distance between the two charges

Therefore;

E = (9 x 10^9) × (0.0042) × (-0.0050) / (0.0030)²  

 = -2.1 x 10^10 N

Therefore; electrical force acting between the two charges is -2.1 x 10^10 N.

6 0
4 years ago
At a given moment in time, instantaneous speed can be thought of as the magnitude of instantaneous
kaheart [24]

At a given moment in time, the instantaneous speed can be thought of as the magnitude of instantaneous velocity.

Instantaneous speed is the magnitude of the instantaneous velocity, the instantaneous velocity has direction but the instantaneous speed does not have any direction. Hence, the instantaneous speed has the same value as that of the magnitude of the instantaneous velocity. It doesn't have any direction.

5 0
3 years ago
Read 2 more answers
Please help, thank you,
Elena-2011 [213]

same, stapler, gravity, motion, acceleration

6 0
3 years ago
Uniform solid sphere of mass M and radius R rotates with an angular speed w about an axis through is center A uniform solid cyli
Maru [420]

Answer:

e. 2ωs / √5

Explanation:

The rotational kinetic energy of any rigid body, like an extension of the translational kinetic energy, is defined as follows:

Krot = 1/2 *I * ω²

For a solid sphere of mass M and radius R, the moment of inertia regarding any axis through its center, is as follows:

I =2/5 M*R²⇒ Krot(sp) = 1/2 (2/5 M*R²)*ωs² (1)

For a solid cylinder, rotating through an axis running through the central axis of the cylinder, the moment of inertia can be calculated as follows:

I = 1/2 M*R² ⇒ Krot(c) = 1/2 (1/2*M*R²)*ωc² (2)

As both rotational kinetic energies must be equal each other, we can equate (1) and (2), as follows:

1/2 (2/5 M*R²)*ωs² = 1/2 (1/2*M*R²)*ωc²

Simplifying common terms, and solving for ωc, we have:

ωc = 2*ωs /√5

4 0
3 years ago
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