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2 years ago

Which statements correctly describe forces? Check all that apply.

Physics

2 answers:

bezimeni [28]2 years ago

8 0

1. Forces have the ability to change an object’s state of motion.

TRUE

As per Newton's first law when unbalanced force act on an object then the state of motion of the object will change.

2. Forces are vectors.

TRUE

Since forces must have direction along with their magnitude so it is vector

3. Forces are measured in joules.

FALSE

Force is measured in Newton in SI unit or we can use kg m/s/s as its unit while Joule is the SI unit to measure energy

4. Forces are measured in newtons.

TRUE

Force is measured in Newton in SI unit system for the honor of Sir Issac Newton

5. Forces can have a positive or negative value to indicate direction.

TRUE

Since force is a vector quantity so it represents positive or negative for the presentation of direction.

Monica [59]2 years ago

4 0

Forces have the ability to change an object's state of motion

Yes, this is obviously TRUE. Right now I am exerting a force on my keyboard which changes the keys state of motion. So this statement is true, forces do have the ability to change an objects state of motion.

2. Forces are vectors

Yes, this statement is TRUE. Forces are vector quantities. A vector quantity is a quantity that contains both a magnitude and direction. In order to describe a force you need to measure/say its magnitude (size) and direction.

3. Forces are measured in Joules

Depends, are we talking electricity or physical force? In this case it is physical force because the question does not include or mention electrical forces. Force is usually measured in Newtons (N) (kg*m/s^2). Therefore this statement is FALSE.

4. Forces are measured in Newtons

Well well well. Where have we seen this before? This statement is TRUE. (since the question isn't describing an electrical force).

5. Forces can have a positive or negative value to indicate direction

This is TRUE, and I have failed countless exams because of it. Just remember, it isn't a negative VALUE necessarily! It is negative because it is indicating DIRECTION. Make sure to read directions on the test to see whether you must include this.

Physics is fun!

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The late news reports the story of a shooting in the city. Investigators think that they have recovered the weapon and they run

Gemiola [76]

Answer:

50000 N

Explanation:

From the question given above, the following data were obtained:

Mass (m) of bullet = 0.050 kg

velocity (v) = 400 m/s

Distance (s) = 0.080 m

Force (F) =?

Next, we shall determine the acceleration of the bullet. This can be obtained as follow:

Initial velocity (u) = 0 m/s

Final velocity (v) = 400 m/s

Distance (s) = 0.080 m

Acceleration (a) =?

v² = u² + 2as

400² = 0 + (2 × a × 0.08)

160000 = 0 + 0.16a

160000 = 0.16a

Divide both side by 0.16

a = 160000 / 0.16

a = 1×10⁶ m/s²

Finally, we shall determine the force exerted by the bullet on the target. This can be obtained as follow:

Mass (m) of bullet = 0.050 kg

Acceleration (a) of bullet = 1×10⁶ m/s²

Force (F) =?

F = ma

F = 0.050 × 1×10⁶

F = 50000 N

Thus, the bullet exerted a force of 50000 N on the target.

7 0

2 years ago

Two ice skaters, Lilly and John, face each other while stationary and push against each others hands. John's mass is twice the m

VladimirAG [237]

Answer:

lily's speed would be twice john's speed

7 0

2 years ago

A person is standing outdoors in the shade where the temperature is 35 °C.

Free_Kalibri [48]

Answer:

(a) Eₐ = 6.36 J/s

(b) Eₐ = 4.64 J/s

Explanation:

Stefan-Boltzmann law: States that the total energy per second radiated or absorbed by a black body is directly proportional to the absolute temperature.

Using, Stefan-Boltzmann equation

Eₐ =eσAT⁴ ................ Equation 1

where Eₐ = Radiant energy absorbed per seconds, e = emissivity, σ = stefan - boltzman constant, A = Surface area. and T = temperature in kelvin

(a) Where e = 0.89, σ = 5.67 ×10⁻⁸ watt/m²/K⁴, A = 140 cm² = 140 cm²(m²/10000cm²) = 0.014 m², T = 35 °C = (35 + 273) K = 308 K.

Applying these values in equation 1 above,

Eₐ = 0.89 × 5.67 ×10⁻⁸ × 0.014 × (308)⁴

Eₐ =6.36 J/s

(b) when e = 0.65,

∴ Eₐ = 0.65 × 5.67 × 10⁻⁸ × 0.014 × (308)⁴

Eₐ = 4.64 J/s

6 0

2 years ago

A sample of silver (with work function Φ=4.52 eV ) is exposed to an ultraviolet light source (????=200 nm), which results in the

Crank

Answer:

1. c

2. e

3. d

Explanation:

From Einstein's Photoelectric Equation, we know that:

Energy given up by photon = Work Function + K.E of Electron

hc/λ = φ + K.E

where,

h = Plank's Constant = 6.626 x 10⁻³⁴ J.s

c = speed of light = 3 x 10⁸ m/s

λ = wavelength of light source = 200 nm = 2 x 10⁻⁷ m

φ = (5.1 eV)(1.6 x 10⁻¹⁹ J/eV) = 8.16 x 10⁻¹⁹ J

Therefore,

(6.626 x 10⁻³⁴ J.s)(3 x 10⁸ m/s)/(2 x 10⁻⁷ m) - 8.16 x 10⁻¹⁹ = K.E

K.E = (9.939 - 8.16) x 10⁻¹⁹ J

K.E = 1.778 x 10⁻¹⁹ J

The positive answer shows that electrons will be emitted. Since it is clear from the equation the the K.E of electron decreases with the increase in work function. Therefore:

c. less energetic photo-electrons (on average)

The increase in light sources means an increase in the intensity of light. The no. of photons are increased, due to increase of intensity. Thus, more photons hit the metal and they eject greater no. of electrons. Therefore,

e. more photo-electrons ejected

X-rays have smaller wavelength and greater energy than ultraviolet rays. Thus, the photons with greater energy will strike the metal and as a result, electrons with higher energy will be ejected.

d. more energetic photo-electrons (on average)

8 0

2 years ago

While Bob is demonstrating the gravitational force on falling objects to his class, he drops an 1.0 lb bag of feathers from the

____ [38]

As per the question Bob drops the bag full with feathers from the top of the building.

The mass of the bag(m)= 1.0 lb

Let the air resistance is neglected.As the bag is under free fall ,hence the only force that acts on the bag is the force of gravity which is in vertical downward direction.

Here the acceleration produced on bag due to the free fall will be nothing else except the acceleration due to gravity i.e g =9.8 m/s^2

Here we are asked to calculate the distance travelled by the bag at the instant 1.5 s

Hence time t= 1.5 s

From equation of kinematics we know that -

S=ut + 0.5at^2 [ here S is the distance travelled]

For motion under free fall initial velocity (u)=0.

Hence S= 0×1.5+{0.5×(-9.8)×(1.5)^2}

⇒ -S =0-11.025 m

⇒ S= 11.025 m

=11 m

Here the negative sign is taken only due to the vertical downward motion of the body .we may take is positive depending on our frame of reference .

Hence the correct option is B.

3 0

2 years ago

Read 2 more answers