Sarah, whose mass is 40 kg, is on her way to school after a winter storm when she accidentally slips on a patch of ice whose coe
1 answer:
Sarah's acceleration is
Explanation:
The force of kinetic friction acting on Sarah has a magnitude which is given by:
where
is the coefficient of kinetic friction
m is Sarah's mass
g is the acceleration of gravity
Moreover, according to Newton's second law of motion, we know that the net force on Sarah is equal to its mass times its acceleration:
where a is the acceleration
Since the force of friction is the only force acting on Sarah, we can say that the net force is equal to the force of friction, therefore:
where the negative sign is due to the fact that the force of friction has a direction opposite to the motion of Sarah. Solving for a, we find
And substituting the following values:
(coefficient of friction)
(acceleration of gravity)
we find:
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In order to determine the required force to stop the car, proceed as follow:
Calculate the deceleration of the car, by using the following formula:
where,
v: final speed = 0m/s (the car stops)
vo: initial speed = 36m/s
x: distance traveled = 980m
a: deceleration of the car= ?
Solve the equation above for a, replace the values of the other parameters and simplify:
Next, consider that the formula for the force is:
where,
m: mass of the car = 820 kg
a: deceleration of the car = 0.66m/s^2
Replace the previous values and simplify:
Hence, the required force to stop the car is 542.20N
Answer
given,
I = 0.140 kg ·m²
decrease from 3.00 to 0.800 kg ·m²/s in 1.50 s.
a)
τ = -1.467 N m
b) angle at which fly wheel will turn
θ = 20.35 rad
c) work done on the wheel
W = τ x θ
W = -1.467 x 20.35 rad
W = -29.86 J
d) average power of wheel