Kelli weighs 420 N, and she is sitting on a playground swing that hangs 0.45 m above the ground. Her mom pulls?
Increase in height = 1.00-0.45 = 0.55m Ep relative to lowest position = weight * height = 420*0.55 = 231J Ek at bottom = 231J Ek = 0.5*m*v² Mass = 420/9.8 = 42.86kg 231 = 0.5*42.86*v² V² = 231/21.43 V² = 10.779 V = 3.28m/s Velocity at bottom of swing is 3.28m/s If velocity at bottom of swing was 2m/s, Ek = 0.5*42.86*2² Ek = 85.72J Loss of energy = 231 - 85.72 = 145.28J The loss of energy, or work done by friction = 145.3J Hakeem Problem: V² = U² +2*a*s 7.6² = U² + 2*9.8*2 57.76 = U² +39.2 U² = 57.76 -39.2 U² = 18.56 U = 4.31m/s downwards velocity.
In the 1950s, an experimental train that had a mass of 2.90 104 kg ?
was powered across a level track by a jet engine that produced a thrust of 4.50 105 N for a distance of 509 m. Assume that air resistance is negligible. (a) Find the work done on the train. answer in J (b) Find the change in kinetic energy. answer in J (c) Find the final kinetic energy of the train if it started from rest. answer in J (d) Find the final speed of the train if there had been no friction. answer in m/s
How can I minimize taxes in retirement?
Building a retirement nest egg requires a lot of careful planning so you don't end up spending your savings too soon. Be wary of taxes as they can accelerate the burn rate of your assets. That's why you should try looking at the types of retirement savings from a tax standpoint. There are 3 types of retirement savings: • Ordinary savings - Income and capital gains are fully taxable • Tax-deferred savings (Employer-sponsored retirement plans and traditional IRAs) - Taxes are not paid until the money is taken out • Tax-exempt savings (Roth individual retirement account (IRA) - Taxes paid upfront so they can now grow tax-free with no further tax due upon withdrawal Financial planners often suggest drawing first from taxable savings in retirement, so you can hold on to assets with favorable tax treatment for a longer time. You need to think about the impact of taxes on retirement accounts before making the decision of withdrawing your savings. Remember you will pay a penalty if you withdraw money from a tax-deferred plan before reaching age 59 1/2. At age 70 1/2, you are required to start taking distributions from a tax-deferred plan, and paying any tax liability that results from those distributions. In between those ages of 59 1/2 and 70 1/2, you have the flexibility to draw on a tax-deferred plan at your discretion. Once you enter this window of time, you have the most latitude to alter your withdrawal strategy to manage your tax liability. Keep in mind that the withdrawals do not necessarily mean you should be spending this money as it comes out. The withdrawal is simply a matter of shifting the money from a tax-advantaged account to a taxable account, but you should still be preserving some of that money for later in retirement. If you have little or no taxable income in retirement, you should be taking small amounts of money out of your tax-deferred plans every year once you reach age 59 1/2. If you limit that amount to the total of your personal exemptions and standard deductions, you can essentially take the money out tax-free. Beyond matching distributions from tax-deferred plans with personal exemptions and standard deductions, there is another option to further limit your tax liability. You can make heavier distributions in years when you have large itemized deductions (such as for medical expenses).
Diverging lens focal length = 6.8cm image distance if object distance = 6.2cm?
The focal length of a converging lens is positive, but for a diverging lens, it is negative, therefore f = -6.8 cm We now use the object image relation for a thin lens (concave or diverging) which is defined by: 1/s + 1/s' = 1/f where s is the object distance, s' is the image distance and f is the focal length, therefore 1/6.2cm + 1/s' = 1/-6.8cm solve for s' and get approx. -3.243cm, which means the image formed is located 3.243cm to the left of the diverging lens if the object is located 6.2cm to the left of the diverging lens. The lateral magnification for a thin lens is defined by m=-s'/s therefore m = -(-3.243cm) / 6.2cm = +0.5231 The magnification is positive, which means the image formed is erect (pointing upwards) if the object is pointing upwards. You can check this by drawing a raw diagram as well. Hope this helps and is correct.