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givi [52]
3 years ago
12

A 180 lb crate is on the ground, and a strong rope is attached. You need to move it across the basement floor, which has a coeff

icient of friction of 0.7 against the wood of the crate. To avoid actually working you call your friend to complain that you have to push it so hard. Your friend says you should pull it with the rope (your height will cause it to have a 60° angle to horizontal), since it will lower the weight and therefore the friction force. You counter (still avoiding work) that you will also have less force on the crate so it cancels out. What is the right answer? Is it better to pull with the rope or push? Why?
Physics
1 answer:
jekas [21]3 years ago
6 0

Answer:

F = 505.13 N

Yes it is better to pull the rope rather than push it

Explanation:

Let the force is applied at an angle of 60 degree

so we will have net vertical force on the crate is given as

F_n + Fsin60 = mg

here we know

m = 180 lb

m = 81.65 kg

F_n = 81.65(9.81) - Fsin60

F_n = 801 - 0.866 F

now friction force on the crate is given as

F_x = \mu F_n

Fcos60 = 0.7(801 - 0.866 F)

0.5F + 0.61F = 560.7

F = 505.13 N

Yes it is better to pull the rope rather than push it

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One of two 25-year-old identical twins begins a trip on a spaceship traveling at 0.8 c while her twin remains on Earth. The twin
borishaifa [10]

Answer:

This equation is based on twin paradox - a phenomena where one of the twin travels to space at a speed close to speed of light and the other remains on earth. the twin from the space on return discovers that the one on earth age faster.

Solution:

t_{o} = 10 years

v = 0.8c

c = speed of light in vacuum

The problem can be solved by time dilation equation:

t = \frac{t_{o}}{\sqrt{1 - \frac{v^{2}}{c^{2}}}}            (1)

where,

t = time observed from a different inertial frame

Now, using eqn (1), we get:

t = \frac{10}{\sqrt{1 - \frac{(0.8c)^{2}}{c^{2}}}}

t = 16.67 years

The age of the twin on spaceship according to the one on earth = 25+16.67 =41.66 years

8 0
3 years ago
Select all of the answers that apply.
galben [10]
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6 0
4 years ago
Read 2 more answers
An ion with charge of Q = +3.2 x 10-19 C is in a region where a uniform electric field of magnitude E = 5.0 X 105 V/m is perpend
san4es73 [151]

Answer:

option C

Explanation:

given,

Q = +3.2 x 10⁻¹⁹ C

E = 5.0 X 10⁵ V/m

B = 0.80 T

ion's acceleration is zero  

when acceleration is zero the magnitude of both the forces becomes equal.

q E = q V B

v = \dfrac{E}{B}

v= \dfrac{5 \times 10^5}{0.80}

v = 6.25 × 10⁵ m/s ≈ 6.3 × 10⁵ m/s

hence, the correct answer is option C

8 0
3 years ago
Which statement accurately describes current electricity?
Colt1911 [192]

Answer:

C. It is caused by flowing negatively charged particles.

Explanation:

Current electricity is caused by flowing negatively charged particles. The negatively charged particles that are responsible for the flow of electricity are called electrons.

The force is equal at all points in the field as the field lines are parallel in a uniform field. So, negatively charged particles will move in the opposite direction to the current.

Hence, the correct answer is "C. It is caused by flowing negatively charged particles."

8 0
3 years ago
A 26-g steel-jacketed bullet is fired with a velocity of 630 m/s toward a steel plate and ricochets along path CD with a velocit
Alecsey [184]

Answer:

  F = - 3.53 10⁵ N

Explanation:

This problem must be solved using the relationship between momentum and the amount of movement.

          I = F t = Δp

To find the time we use that the average speed in the contact is constant (v = 600m / s), let's use the uniform movement ratio

        v = d / t

        t = d / v

Reduce SI system

          m = 26 g ( 1 kg/1000g) = 26 10⁻³ kg

          d = 50 mm ( 1m/ 1000 mm) = 50 10⁻³ m

Let's calculate

         t = 50 10⁻³ / 600

         t = 8.33 10⁻⁵ s

With this value we use the momentum and momentum relationship

        F t = m v - m v₀

As the bullet bounces the speed sign after the crash is negative

       F = m (v-vo) / t

       F = 26 10⁻³ (-500 - 630) / 8.33 10⁻⁵

       F = - 3.53 10⁵ N

The negative sign indicates that the force is exerted against the bullet

5 0
3 years ago
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