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4 years ago

3. Can there be forces acting on an object at rest? Explain why or why not.

1 answer:

3 0

Yes, because gravity always exerts a force whether an object is at rest or in motion. Gravity is the reason we aren’t all floating as cool as that would be we would probably be hit by a plane

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If the numbers on the plate are 6.0 cm apart, and the spy satellite is at an altitude of 160 km , what must be the diameter of t

Alexxx [7]

Answer:

The diameter of the camera aperture must be greater than or equal to 1.49m

Explanation:

Let the distance separating two objects, x = 6.0 cm = 0.06 m

The distance between the observer and the two objects, d = 160 km = 160000 m

Let ∅ = minimum angular separation between the two objects that the satellite can resolve

tan( ∅) = x/d

Since there is minimum angular separation, tan( ∅) ≈∅

∅ = x/d

∅ = 0.06/160000

∅ = 3.75 * 10⁻⁷rad

For the satellite to be able to resolve the objects,

D ≥ 1.22λ/∅

λ = 560 nm = 560 * 10⁻⁹

D ≥ 1.22 * (560 * 10⁻⁹)/(3.75 * 10⁻⁷)

D ≥ 149.33 * 10⁻² m

D ≥ 1.49 m

7 0

3 years ago

A truck with a mass of 1810 kg and moving with a speed of 16.0 m/s rear-ends a 673-kg car stopped at an intersection. The collis

nadezda [96]

Answer:

velocity of truck = 7.32 m/s

velocity of truck = 23.32 m/s

Explanation:

mass of truck, M = 1810 kg

initial velocity of truck, U = 16 m/s

mass of car, m = 673 kg

initial velocity of car, u = 0 m/s

Let the final speed of the car is v and the final speed of truck is V.

Use conservation of momentum

Momentum before collision = Momentum after collision

M x U + m x 0 = M x V + m x v

1810 x 16 + 0 = 1810 V + 673 v

28960 = 1810 V + 673 v .... (1)

As the collision is elastic, so the coefficient of restitution is 1.

By using the formula

$e=\frac{v_{1}-v_{2}}{u_{2}-u_{1}}$

where, u1 be the initial velocity of truck, u2 be the initial velocity of the car, v1 be the final velocity of truck and v2 be the final velocity of car.

$1=\frac{V - v}}{0-U}$

V - v = - U

V - v = - 16

v - V = 16

v = 16 + V

Substitute in equation (1), we get

28960 = 1810 V + 673 (16 + V)

28960 = 1810 V + 10768 + 673 V

18192 = 2483 V

V = 7.32 m/s

v = 16 + 7.32 = 23.32 m/s

Thus, the velocity of truck after collision is 7.32 m/s and the velocity of car after collision is 23.32 m/s.

4 0

3 years ago

True or False? A model train traveling at a constant speed around a circular track has a constant velocity.

RSB [31]

For both, remember that velocity is a vector force, meaning that it has both a magnitude and direction. Since direction is part of the vector, if the direction changes so does the velocity in general. The changing of velocity is acceleration, so for 1 the answer is False.
For 2 I'm not sure what you meant, but the answer is the acceleration changes but the velocity does not.

8 0

3 years ago

Read 2 more answers

Which type of telescope does not require darkness in order to be able to use it?

exis [7]

Answer:

A type of telescope that does not require darkness in order to be able to use it is the refracting telescope

Explanation:

A refracting telescope consists of a lens and an eyepiece collects light which is then focused to present a magnified, bright and clear image.

The incident light on a refracting telescope is bent by refraction such that the light is focused to the focal point.

In refracting telescopes, the image is formed by bending light, that is by refraction.

The refracting telescope technology has been applied to binoculars and camera zoom lenses.

5 0

3 years ago

A car of mass 1000 kg is moving at 25 m/s. It collides with a car of mass 1200 kg

max2010maxim [7]

Answer:

Explanation:

As momentum is a vector, we cannot tell for sure.

It will be bracketed between a maximum of

1000(25) + 1200(30) = 61000 kg•m/s

if both cars are moving in the same direction before collision

and a minimum of

1200(30) + 1000(-25) = 11000 kg•m/s

if the cars are in for a head on collision.

It could have a magnitude anywhere between these two limits for a collision angle 0<θ<180°

7 0

3 years ago