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3 years ago

A car traveling at a speed of 30 m/s encounters an emergency and comes to a complete

Physics

1 answer:

Natasha2012 [34]3 years ago

4 0

Answer:

Explanation:

Use the one-dimensional equation

$v_f=v_0+at$ which says that the final velocity of an object is equal to the object's initial velocity plus its acceleration times time. We are looking for time. That means the equation looks like this:

0 = 30 + (-4)t and

-30 = -4t so

t = 7.5 sec

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A worker lifts a 20.0-kg bucket of concrete from the ground up to the top of a 25.0-m tall building. The bucket is initially at

yuradex [85]

Answer:

Minimum work = 5060 J

Explanation:

Given:

Mass of the bucket (m) = 20.0 kg

Initial speed of the bucket (u) = 0 m/s

Final speed of the bucket (v) = 4.0 m/s

Displacement of the bucket (h) = 25.0 m

Let 'W' be the work done by the worker in lifting the bucket.

So, we know from work-energy theorem that, work done by a force is equal to the change in the mechanical energy of the system.

Change in mechanical energy is equal to the sum of change in potential energy and kinetic energy. Therefore,

$\Delta E=\Delta U+\Delta K\\\\\Delta E= mgh+\frac{1}{2}m(v^2-u^2)$

Therefore, the work done by the worker in lifting the bucket is given as:

$W=\Delta E\\\\W=mgh+\frac{1}{2}m(v^2-u^2)$

Now, plug in the values given and solve for 'W'. This gives,

$W=(20\ kg)(9.8\ m/s^2)(25\ m)+\frac{1}{2}(20\ kg)(4^2-0^2)\ m^2/s^2\\\\W=4900\ J +160\ J\\\\W=5060\ J$

Therefore, the minimum work that the worker did in lifting the bucket is 5060 J.

7 0

2 years ago

The acceleration due to gravity on the surface of Jupiter is about 2.5 times the acceleration due to gravity on Earth’s surface.

melisa1 [442]

The answer is 2.5 times heavier than on Earth !!

so the answer is C !!

4 0

2 years ago

Read 2 more answers

In the heat equation, what does c represent

Bingel [31]

Heat equation, Q = m.c.Δt
Here, c represents " the specific heat of the substance "

Hope this helps!

5 0

3 years ago

Read 2 more answers

In a circuit, a variable resistor is to be connected across a potential difference of 60 volts to allow the current to be adjust

sweet [91]

Answer:

600 and 1500 [ohm

Explanation:

To solve this problem we must use ohm's law, which tells us that the voltage is the product of the current by the resistance, so we have:

V = I*R

where:

V = voltage [V]

I = current [amp]

R = resistance [ohm]

<u>Therefore:</u>

R = V/I

R1 = 60/(40*10^-3) = 1500 [ohm]

R2 = 60/(100*10^-3) = 600 [ohm]

So the resistance should be among 600 and 1500 [ohm]

4 0

3 years ago

Does coefficient of linear expansion depends on length

nlexa [21]

Answer:

yes

Explanation:

As the formula is α= ΔL/L*ΔT where alpha (α) is the sign of coefficient of linear expansion

5 0

2 years ago