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2 years ago

.A box falls to the ground from a delivery truck traveling at 30 m/s. After hitting the road, it slides 45 m to

Physics

1 answer:

Romashka-Z-Leto [24]2 years ago

8 0

Answer:

t = 3 seconds

Explanation:

Given that,

Initial speed, u = 30 m/s

Final speed, v = 0

It slides 45 m to rest.it take the box to come to rest

We need to find how long it take the box to come to rest.

Let a be the acceleration and t is time.

$v^2-u^2=2ad\\\\a=\dfrac{v^2-u^2}{2d}\\\\a=\dfrac{(30)^2-u^2}{2(45)}\\\\=10\ m/s^2$

Now finding time.

$t=\dfrac{v-u}{a}\\\\t=\dfrac{30-0}{10}\\\\t=3\ s$

So, the required time is 3 seconds.

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If a racecar traveling at 6 m/s accelerates at 0.75 m/s over 30 seconds, what is its

Elina [12.6K]

Answer:

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Explanation:

8 0

3 years ago

Suppose that a steel bridge, 1000 m long, were built without any expansion joints. Suppose that only one end of the bridge was h

Stels [109]

Answer:

The difference in the length of the bridge is 0.42 m.

Explanation:

Given that,

Length = 1000 m

Winter temperature = 0°C

Summer temperature = 40°C

Coefficient of thermal expansion $\alpha= 10.5\times10^{-6}\ K^{-1}$

We need to calculate the difference in the length of the bridge

Using formula of the difference in the length

$\Delta L=L\alpha\Delta T$

Where, $\Delta T$ = temperature difference

$\alpha$ =Coefficient of thermal expansion

L= length

Put the value into the formula

$\Delta L=1000\times10.5\times10^{-6}(40^{\circ}-0^{\circ})$

$\Delta L=0.42\ m$

Hence, The difference in the length of the bridge is 0.42 m.

5 0

2 years ago

Does the air exert a buoyant force on all objects in air or only on objects such as balloons that are very light for their size?

Citrus2011 [14]

Answer:

See explanation

Explanation:

Solution:-

Buoyancy is the force that causes objects to float. It is the force exerted on an object that is partly or wholly immersed in a fluid. Buoyancy is caused by the differences in pressure acting on opposite sides of an object immersed in a static fluid. It is also known as the buoyant force. Buoyancy is the phenomena due to Buoyant Force.

It is as an upward force exerted by a fluid that opposes the weight of an object immersed in a fluid. As we know, the pressure in a fluid column increases with depth. Thus, the pressure at the bottom of an object submerged in the fluid is greater than that at the top. The difference in this pressure results in a net upward force on the object which we define as buoyancy.

- The formula for buoyant force (Fb) is given:

Fb = ρ*g*V

- The force acts on all objects. However, it depends on the fluid density and amount of volume displaced.

- The Buoyant force exerted by air with density = 1.225 kg/m^3 on an object with volume (V) is:

Fb = ρ*g*V = 1.225*9.81*V = 12.02*V

- For the similar object with mass (m), the downward weight would be:

W = m*g

- For the object to float the buoyant force (Fb) must be greater than weight of the object:

Fb > W

12.02*V > m*9.81

V / m > 0.816

- The ratio of V / m must be at-least = 0.816.

- Assuming the object is fully immersed in air, then the volume displaced V = ρ_material*V

ρ_material < 1 / 0.816

ρ_material < 1.225 or ( ρ_air )

- So the for an object to float in air its material density must always be less than that of air. That why in balloons lighter gas is used which have density less than that of air like Helium.

4 0

3 years ago

In order to do work, the force vector must be

gregori [183]

As we know that total work done by a force is given by

$W = F.d$