Answer:
C.
Explanation:
A person pushing a couch will face resistive force of friction . When resistive force is greater then his force of effort , couch will not move. This force is static friction because the couch is stationary. When the force of effort is increased , magnitude of static friction also increases keeping the couch stationary. The ability of the static friction to increase its magnitude is limited by a maximum value beyond which the couch starts moving. The static friction is then converted into kinetic friction.
In rest of the three cases object is already moving so kinetic friction is in action.
The speed is
v = 5t² + 4t
where
v is in m/s, and t in s.
The acceleration is the derivative of the velocity. It is
a = 10t + 4
When t = 2 s, the acceleration is
a(2) = 10*2 +4 = 24 m/s²
Answer: 24 m/s²
Answer:
Explanation:
The period of a simple pendulum is given by:
where
L is the length of the pendulum
g is the acceleration of gravity
From this equation we can write
Taking the square of this equation, we get:
So we see that 
is proportional to L and inversely proportional to g. So, we can write:
So the only correct option is
I'm not sure that's true ... we'd need to see some numbers.
But if it is true, it's the same reason why some places don't
want ladies to walk on their floors with high heels.
Pressure is (weight) divided by (area).
Pressure exerted
by a ballerina = (ballerina's weight)/(area of her toe on the floor)
Pressure exerted
by an elephant = (elephant's weight)/(area of 4 elephant feet)
Pressure exerted by
a lady in high heels = (lady's weight) / (area of 1 or 2 heels)
You can see that the greatest weight might not exert the greatest
pressure, and the smallest weight might not exert the smallest
pressure. The area is important, and it takes an awful lot of toes
or high heels to equal the area of one or more elephant's feet.
