The velocity and acceleration of an object
1.must have the same sign.
2.can have opposite signs.
3.must both be zero simultaneously; one cannot be zero and the other nonzero.
4.must have opposite signs.
2
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Length Contraction: A spacecraft is measured by a scientist on the ground to have a length of 81 m as it flies overhead with a speed 2.4 × 108 m/s. The spacecraft then lands and its length is again measured by the scientist at rest on the ground. What result does he now get for the length of the spacecraft? (c = 3.0 × 108 m/s)
Fill in the blank(s) with the appropriate word(s).
A 5.0-?C point charge is placed at the 0.00 cm mark of a meter stick and a -4.0-?C point charge is placed at the 50 cm mark. At what point on a line joining the two charges is the electric field due to these charges equal to zero?
What will be an ideal response?
A metal or ceramic composed of many small crystals is a(n) ______________.
Fill in the blank(s) with the appropriate word(s).
The observed amount of difference between the perihelion of Earth in early January and aphelion in early July results in the northern hemisphere being _____
a. cold in January and hot in July b. hot in January and cold in July c. equally cold in both January and July d. equally hot in bot January and July e. Wrong! The seasonal differences in northern hemisphere temperatures is not caused by differences in distance from the Sun.