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3 years ago

5

The force that keeps two surfaces at rest from sliding over each other is

1 answer:

natka813 [3]3 years ago

8 0

Friction is the correct answer.

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A car moves at a speed of 50 kilometers/hour. Its kinetic energy is 400 joules. If the same car moves at a speed of 100 kilomete

HACTEHA [7]

Explanation :

Speed of car, $v_1=50\ km/h=13.8\ m/s$

Kinetic energy of the car, $KE_1=400\ J$

Speed of car, $v_2=100\ km/h=27.7\ m/s$

Let $KE_2$ is the kinetic energy of the car when it is moving with 100 km/h.

$\dfrac{KE_1}{KE_2}=\dfrac{\dfrac{1}{2}mv_1^2}{\dfrac{1}{2}mv_2^2}$

$\dfrac{KE_1}{KE_2}=\dfrac{v_1^2}{v_2^2}$

$KE_2=KE_1(\dfrac{v_2}{v_1})^2$

$KE_2=400\ J\times (\dfrac{27.7\ m/s}{13.8\ m/s})^2$

$KE_2=1611.6\ J$

Initial velocity of both cars are 0. Using third equation of motion :

So, $S_1=\dfrac{v_1^2}{2a}=\dfrac{v_1t}{2}=\dfrac{v_1t}{2}$

and $S_2=\dfrac{v_2^2}{2a}=\dfrac{v_2t}{2}=\dfrac{v_2t}{2}$

t is same. So,

$\dfrac{S_1}{S_2}=\dfrac{50\ m/s}{100\ m/s}$

$\dfrac{S_1}{S_2}=\dfrac{1}{2}$

$S_2=2\ S_1$

So, the braking distance at the faster speed is twice the braking distance at the slower speed.

4 0

4 years ago

Read 2 more answers

Water is pouring into a conical tank at the rate of 8 cubic feet per minute. If the height of the tank is 10 feet and the radius

iren [92.7K]

Answer:

$\frac{25}{8\pi}ft/min$

Explanation:

We are given that

$\frac{dV}{dt}=8 ft^3/min$

Height of tank=h=10 ft

Radius of tank, r=4 feet

We have to find the dh/dt when the water is 4 feet deep.

$\frac{r}{h}=\frac{4}{10}=\frac{2}{5}$

$r=\frac{2}{5}h$

Volume of cone , $V=\frac{1}{3}\pi r^2 h$

Substitute the values

Volume of cone , $V=\frac{1}{3}\pi(\frac{2}{5}h)^2h=\frac{4}{75}\pi h^3$

Differentiate w.r.t t

$\frac{dV}{dt}=\frac{12}{75}\pi\times h^2\times \frac{dh}{dt}$

Substitute the values

$8=\frac{12}{75}\times\pi (4)^2\times \frac{dh}{dt}$

$\frac{dh}{dt}=\frac{8\times 75}{12\times 16\pi}=\frac{25}{8\pi}ft/min$

3 0

4 years ago

How many miles does hubble circle above our planet?

Lyrx [107]

547 kilometres, or 340 miles

6 0

3 years ago

if a certain car, going with speed v1, rounds a level curve with a radius r1, it is just on the verge of skidding. if its speed

schepotkina [342]

Answer:

The correct answer is 4R1

Explanation:

According to the given scenario ,the radius of the tightest curve on the same road without skidding is as follows:

As we know that

Centeripetal Acceleration is

= v^2 ÷ r

In the case when velocity becomes 2 times so the r would be 4 times

So, the radius of the tightest curve on the same road without skidding is 4R1

3 0

4 years ago

Justine is ice-skating at the Lloyd Center. What is her final velocity if she accelerates at a rate of 2.0 m/s for 3.5 seconds?

belka [17]

Answer:

7 m/s

Explanation:

Acceleration, $a=\frac {v-u}{t}$

Where v and u are the final and initial velocities of the Justine respectively, t is the time taken for Justin to attain final velocity.

Making v the subject then

v=at+u

Taking u as zero then

Substituting 3.5 for t, 2 as a then

v=3.5*2=7 m/s

8 0

3 years ago