For uniform acceleration (or deceleration in this case), you use the formula:
Vf = Vi + at
Vi = 22 m/s
Vf = 0 (coming to a stop)
t = 5 sec
Plugging everything into the formula gives you:
0 = 22 + 5a
-22 = 5a
a = -22/5 or -4.4 m/s^2
Hope this helps!
How much gravitational potential energy does the block have
when it gets to the top of the ramp ?
(weight) x (height) = (15 N) x (0.2 m) = 3 Joules .
If there were no friction, you would only need to do 3 Joules of work
to lift the block from the bottom to the top.
But the question says you actually have to do 4 Joules of work
to get the job done.
Friction stole one of your Joules along the way.
Choice-4 is not the correct one.
Choice-1 is the correct one.
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Notice that the mass of the block is NOT 15 kg , and you
don't have to worry about gravity to answer this question.
The formula for potential energy is (m)·(g)·(h) .
But (m·g) is just the WEIGHT, and the formula
is actually (weight)·(height).
The question GIVES us the weight of the block . . . 15 N .
So the potential energy at the top is just (15N)·(0.2m) = 3 Joules.
Test:
Performing a Litmus Test
Result:
Litmus paper gives the user a general indication of acidity or alkalinity as it correlates to the shade of red or blue that the paper turns.
- To test the pH of a substance, dip a strip of litmus paper into the solution or use a dropper or pipette to drip a small amount of solution onto the litmus paper.
- Blue litmus paper can indicate an acid with a pH between 4 and 5 or lower.
- Red litmus paper can show a base with a pH greater than 8.
- If a solution has a pH between 5 and 8, it will show little color change on the litmus paper.
- A base tested with blue litmus paper will not show any color change, nor will an acid tested with red litmus paper register a change in color.