Something about the earth's surface (land or water) changes

When Marie sees the red traffic light, Marie brakes to a halt from a speed of 70 m/s in just 2 seconds. What is her deceleration

SashulF [63]

Answer:

-35 $m/s^2$

Explanation:

Deceleration is the complete opposite of acceleration and is calculated by adding a negative sign to the formula for finding acceleration.

Since acceleration is calculated by diving the change in velocity with time, deceleration will become:

Deceleration = -Δv/t, where Δv = change in velocity and t = time

In this case, Δv = 70 m/s and t = 2 s, hence;

Deceleration = -70/2 = -35 $m/s^2$

The deceleration is 35 $m/s^2$ .

7 0

3 years ago

A 3.00 × 10^-6 kg ant rides the second hand of an enormous vertical wall clock. The ant smoothly sweeps a circle of radius 50.0

kotykmax [81]

Answer:

1.65×10⁻⁶ N

Explanation:

m = Mass of ant = $3\times 10^{-6}\ kg$

r = Radius = 50 m

t = Time taken to complete on rotation = 60 seconds

Angular velocity

$\omega=\frac{2\pi}{t}\\\Rightarrow \omega=\frac{2\pi}{60}$

Centripetal acceleration is force that is acting outward

$F_c=m\omega^2r\\\Rightarrow F_c=3\times 10^{-6}\times \left(\frac{2\pi}{60}\right)^2\times 50\\\Rightarrow F_c=1.65\times 10^{-6}\ N$

The magnitude of the upward force felt by the ant due to the second hand would be 1.65×10⁻⁶ N

4 0

3 years ago

A meteorologist plans to release a weather balloon from ground level, to be used for high-altitude atmospheric measurements. The

Slav-nsk [51]

Answer:

563.86 N

Explanation:

We know the buoyant force F = weight of air displaced by the balloon.

F = ρgV where ρ = density of air = 1.29 kg/m³, g = acceleration due to gravity = 9.8 m/s² and V = volume of balloon = 4πr/3 (since it is a sphere) where r = radius of balloon = 2.20 m

So, F = ρgV = ρg4πr³/3

substituting the values of the variables into the equation, we have

F = 1.29 kg/m³ × 9.8 m/s² × 4π × (2.20 m)³/3

= 1691.58 N/3

= 563.86 N

8 0

3 years ago

A rock slides down from A to B along the inside surface of a frictionless hemispherical bowl. As the rock slides, mechanical ene

DIA [1.3K]

Answer:

the normal force on the rock acts perpendicular to the bowl's surface.

Explanation:

As we know that Normal force is the reaction force of two contact surfaces which always act perpendicular to the contact surfaces

Here we know that the rock is moving inside the bowl

So Normal force on the rock must perpendicular to the surface of the bowl which always passes through the center of the bowl.

Since the rock is moving in vertical plane so it must have two acceleration

1) Tangential acceleration which will increase the magnitude of the speed along the tangential path

2) Centripetal acceleration which will change the direction of the rock

So here only correct option will be

the normal force on the rock acts perpendicular to the bowl's surface.

6 0

3 years ago

What mass of a material with density rho is required to make a hollow spherical shell having inner radius r1 and outer radius r2

Margarita [4]

Answer:

$m=\rho\times \frac{4}{3} \times \pi \times(r_2^3-r_1^3 )$

Explanation:

We have to make a hollow sphere of inner radius $r_1$ and outer radius $r_2$ .

Then the mass of the material required to make such a sphere would be calculated as:

Total volume of the spherical shell:

$V_t=\frac{4}{3} \pi.r_2^3$

And the volume of the hollow space in the sphere:

$V_h=\frac{4}{3} \pi.r_1^3$

Therefore the net volume of material required to make the sphere:

$V=V_t-V_h$

$V=\frac{4}{3} \pi(r_2^3-r_1^3)$

Now let the density of the of the material be $\rho$ .

Then the mass of the material used is:

$m=\rho.V$

$m=\rho\times \frac{4}{3} \times \pi \times(r_2^3-r_1^3 )$

4 0

4 years ago