10 CHE COSA SUCCEDE SE Un metodo di potenziamento muscolare consiste nel correre con una massa aumenta- ta, in modo da abituare i muscoli a sostenere una mas- sa maggiore. Giada ha una massa di 50 kg e scatta con un'accelerazione di \( 2,0 \mathrm{~m} / \mathrm{s}^{2} \). Ora Giada indossa un busto di 10 kg : quanta forza in più devono imprimere i suoi muscoli per scattare con la stessa accelerazione?

(b.) student : (1) My Day 9. An airplane starts from rest and accelerates at a constant rate of \( 3.00 \mathrm{~m} / \mathrm{s}^{2} \) for 30.0 s before leaving the ground. a. How far did it move? b. How fast was it going when it took off? 10. A brick is dropped from a high scaffold. a. What is its velocity after 4.0 s ? b. How far does the brick fall during this time? 11. A tennis ball is thrown straight up with an initial speed of \( 22.5 \mathrm{~m} / \mathrm{s} \). It is caught at the same distance above the ground. a. How high does the ball rise? b. How long does the ball remain in the air?

1.10 How much energy in kWh is needed to keep a 60 W light on for 8 hours A 48 kWh B \( 4,8 \mathrm{kWh} \) C \( 0,48 \mathrm{kWh} \) D 480 kWh

20. Assuming equal rates of uniform acceleration in both cases, how much further would you travel if braking from \( 56 \mathrm{~m} / \mathrm{s} \) to rest than from \( 28 \mathrm{~m} / \mathrm{s} \) ? \( \begin{array}{llll}\text { A) } 4 \text { times farther } & \text { B) } 3.2 \text { times farther } & \text { C) } 4.8 \text { times farther } & \text { D) } 5.2 \text { times farther } \\ \text { 21. An object is moving in a straight line with constant acceleration. Initially it is traveling at } 16 \mathrm{~m} / \mathrm{s} .\end{array} \) \( \begin{array}{llll}\text { Three seconds later it is traveling at } 10 \mathrm{~m} / \mathrm{s} \text {. How far does it move during this time? } \\ \begin{array}{llll}\text { () } 30 \mathrm{~m} & \text { B) } 39 \mathrm{~m} & \text { C) } 48 \mathrm{~m} & \text { D) } 57 \mathrm{~m}\end{array}\end{array} \).

22. An object is moving with constant non-zero acceleration in the \( +x \) direction. The position versus time graph of this object is \( \begin{array}{ll}\text { A) a horizontal straight line. } & \text { B) a vertical straight line. } \\ \text { C) a straight line making an angle with the time axis. } & \text { D) a parabolic curve. } \\ \text { 23. An object is moving with constant non-zero acceleration in the }+x \text { direction. The velocity versus } \\ \text { time graph of this object is } & \text { B) a vertical straight line. } \\ \begin{array}{ll}\text { A) a horizontal straight line. } & \text { D) a parabolic curve. }\end{array}\end{array} \).

En una papelería se utilizan los siguientes ele- mentos diariamente: dos fotocopiadoras que consumen 650 W en una hora cada una, tres computadores que consumen 1.200 W en 2 h , un fax 450 W en 1,5 h y dos bombillos de 100 W des- de las 5:30 p.m. hasta las 8:00 p.m. Si la papelería abre de lunes a viernes, de 7:00 a.m a 8:00 p.m.: a. ¿cuál es la energía consumida por cada ele- mento diariamente? b. ¿cuál es la energía total consumida a la se- mana? c. ¿cuál es el costo de la energía consumida en un mes, si el valor del kW -h es de \( \$ 331,39 \) ?