The following conversions occur frequently in physics and are very useful. (a) Use 1 mi = 5280 ft and 1 h = 3600 s to convert 60 mph to units of ft/s. (b) The acceleration of a freely falling object is 32 ft/s2. Use 1 ft = 30.48 cm to express this acceleration in units of m/s2. (c) The density of water is 1.0 g/cm3. Convert this density to units of kg/m3.
(a) The velocity in ft/s is 88 ft/s.
(b) The acceleration in m/s2 is 18.3 m/s2.
(c) The density in kg/m3 is 1000 kg/m3.
The conversion in ft/s is shown below,
Thus, the value in ft/s is 88 ft/s.
The conversion in m/s2 is shown below,
Thus, the value in m/s2 is 18.3 m/s2
The conversion in kg/m3 is shown below,
Thus, the value of density in kg/m3 is 1000 kg/m3.
Hot Jupiters. In 2004 astronomers reported the discovery of a large Jupiter-sized planet orbiting very close to the star (hence the term “hot Jupiter”). The orbit was just the distance of Mercury from our sun, and it takes the planet only days to make one orbit (assumed to be circular). (a) What is the mass of the star? Express your answer in kilograms and as a multiple of our sun’s mass. (b) How fast (in km>s) is this planet moving?
A small rock is thrown vertically upward with a speed of 22.0 m/s from the edge of the roof of a 30.0-m-tall building. The rock doesn’t hit the building on its way back down and lands on the street below. Ignore air resistance. (a) What is the speed of the rock just before it hits the street? (b) How much time elapses from when the rock is thrown until it hits the street?
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