20 POINTS: Why does the initial hill of a roller coaster need to be steep?
2 answers:
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Answer:
(A) -2940 J
(B) 392 J
(C) 212.33 N
Explanation:
mass of bear (m) = 25 kg
height of the pole (h) = 12 m
speed (v) = 5.6 m/s
acceleration due to gravity (g) = 9.8 m/s
(A) change in gravitational potential energy (ΔU) = mg(height at the bottom- height at the top)
height at the bottom = 0
= 25 x 9.8 x (0-12) = -2940 J
(B) kinetic energy of the Bear (KE) =
= = 392 J
(C) average frictional force =
- change in KE (ΔKE) = initial KE - final KE
- ΔKE =
-
- when the Bear reaches the bottom of the pole, the final velocity (Vf) is 0, therefore the change in kinetic energy becomes ΔKE =
- 0 = 392 J
\frac{-(ΔKE+ΔU)}{h}[/tex] =
= = 212.33 N
Answer:
D) 11 m/s
Explanation:
The problem asks us to calculate the velocity of the hot dog with respect to the observer stationary outside the train. This velocity is given by:
where
is the velocity of the train (towards right)
is the velocity of the man (towards right)
is the velocity of the hot-dog (towards left, so we put a negative sign)
Substituting the numbers into the equation, we find
and the positive sign means the velocity is toward right.
Answer:
.
Explanation:
By Newton's Second Law, the acceleration of an object is proportional to the net force
on it. In particular, if the mass of the object is
, then
.
Rewrite this equation to obtain:
.
In this case, the assumption is that the force is the only force that is acting on the object. Hence, the net force
on the object would also be
Make sure that all values are in their standard units. Forces should be in Newtons (same as , and the acceleration of the object should be in meters-per-second-squared (
). Apply the equation
to find the mass of the object.
.