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3 years ago

A 75.0-kg person climbs stairs, gaining 2.50 m in height. Find the work done to accomplish this task.

Physics

1 answer:

ololo11 [35]3 years ago

4 0

Answer:

$W=1837.5J$

Explanation:

A force exerts work when there is a displacement of its point of application in the direction of that force. Therefore, the work done by a system is defined as the inner product between the applied force and the displacement:

$W=\vec{F}\cdot \vec{d}\\W=Fcos\theta d$

In this case, we have:

$F=mg\\h=dcos\theta$

So, replacing this:

$W=mgh\\W=75kg*9.8\frac{m}{s^2}*2.5m\\W=1837.5J$

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alisha [4.7K]

Depends on the sandwich, PB&J requires peanut butter and jelly and a butter knife and a piece of bread.

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3 years ago

A car is traveling at 20 meters/second and is brought to rest by applying brakes over a period of 4 seconds. What is its average

frez [133]

(u) = 20 m/s
(v) = 0 m/s
 (t) = 4 s

0 = 20 + a(4)

4 x a = -20

so, the answer is -5 m/s^2. or -5 meter per second

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3 years ago

Read 2 more answers

Gayle runs at a speed of 3.85 m/s and dives on a sled, initially at rest on the top of a frictionless snow-covered hill. After s

enot [183]

Answer:

Final velocity at the bottom of hill is 15.56 m/s.

Explanation:

The given problem can be divided into four parts:

1. Use conservation of momentum to determine the speed of the combined mass (Gayle and sled)

From the law of conservation of momentum (perfectly inelastic collision), the combined velocity is given as:

$p_i = p_f$

$m_1u_1 + m_2v_2 = (m_1 + m_2)v$

$v = \frac{(m_1u_1 + m_2v_2)}{(m_1 + m_2)}$

$v=\frac{[50.0\ kg)(3.85\ m/s) + 0]}{(50.0\ kg + 5.00\ kg)}= 3.5\ m/s$

2. Use conservation of energy to determine the speed after traveling a vertical height of 5 m.

The velocity of Gayle and sled at the instant her brother jumps on is found from the law of conservation of energy:

$E(i) = E(f)$

$KE(i) + PE(i) = KE(f) + PE(f)$

$0.5mv^2(i) + mgh(i) = 0.5mv^2(f) + mgh(f)$

$v(f) = \sqrt{[v^2(i) + 2g(h(i) - h(f))]}$

Here, initial velocity is the final velocity from the first stage. Therefore:

$v(f) = \sqrt{[(3.5)^2+2(9.8)(5.00-0)]}= 10.5\ m/s$

3. Use conservation of momentum to find the combined speed of Gayle and her brother.

Given:

Initial velocity of Gayle and sled is, $u_1(i)=10.5$ m/s

Initial velocity of her brother is, $u_2(i)=0$ m/s

Mass of Gayle and sled is, $m_1=55.0$ kg

Mass of her brother is, $m_2=30.0$ kg

Final combined velocity is given as:

$v(f) = \frac{[m_1u_1(i) + m_2u_2(i)]}{(m_1 + m_2)}$

$v(f)=\frac{[(55.0)(10.5) + 0]}{(55.0+30.0)}= 6.79$ m/s

4. Finally, use conservation of energy to determine the final speed at the bottom of the hill.

Using conservation of energy, the final velocity at the bottom of the hill is:

$E(i) = E(f)$

$KE(i) + PE(i) = KE(f) + PE(f)$

$0.5mv^2(i) + mgh(i) = 0.5mv^2(f) + mgh(f)$

$v(f) = \sqrt{[v^2(i) + 2g(h(i) - h(f))]} \\v(f)=\sqrt{[(6.79)^2 + 2(9.8)(15 - 5.00)]}\\v(f)= 15.56\ m/s$

6 0

2 years ago

If the price of gasoline at a particular station in Europe is 5 euros per liter. An American student in Europe is allowed to use

Mashcka [7]

Answer:

Number of gallons =2 gallon

Explanation:

given data:

rate of gasoline ineurope = 5 euro per liter

total money to buy gasoline = 40 euro

total gasoline an american can buy in europe $= \frac{40}{5}$

= 8 litres of gasoline

As given in the question 1 ltr is 1 quarts therefore

Total no. of quarts is 8 quarts

As from question 4 quarts is equal to one gallon, hence

Number of gallons $= \frac{8}{4} = 2 gallon$

5 0

3 years ago

A fire helicopter carries a 700-kg bucket of water at the end of a 20.0-m long cable. Flying back from a fire at a constant spee

rodikova [14]

Answer:

F = 50636.873 N

Explanation:

given,

bucket of water = 700-kg

length of cable = 20 m

Speed = 40 m/s

angle of the cable = 38.0°

let air resistance be = F

tension in rope be = T

T cos 38° = m×g..................(1)

$T sin 38^0= \dfrac{mv^2}{l} + F$ ..........(2)

equation (1)/(2)

$tan 38^0 =\dfrac{\dfrac{mv^2}{l} + F}{mg}$

$0.781=\dfrac{\dfrac{700\times 40^2}{20} + F}{700\times 9.8}$

F = 50636.873 N

Hence the force exerted on the bucket is equal to F = 50636.873 N

5 0

2 years ago