Answer:
False
Explanation:
The given statement "Two objects must be in contact for them to exert a force on each other" is not true as there are many types of forces that doesn't require being in contact for exerting a force.
One such example is the gravitational force acting between two bodies. Gravitational force is the force of pull with which a body pulls another body without being in contact.
For two bodies of masses 'M' and 'm' separated at a distance of 'R', the gravitational force is given as:
The gravitational force acts always act between bodies that have mass. The bodies are not in contact yet experience force.
Therefore, the given statement is false.
Correct question is;
A ballet dancer spins with 2.4 rev/s with her arms outstretched,when the moment of inertia about axis of rotation is I. With her arms folded,the moment of inertia about the same axis becomes 0.6I about the same axis. Calculate the new rate of spin.
Answer:
4 rev/s
Explanation:
We are given;
Initial Angular velocity; ω_i = 2.4 rev/s
Initial moment of inertia; I_i = I
Final moment of inertia; I_f = 0.6I
From conservation of angular momentum, we have;
I_i × ω_i = I_f × ω_f
Where ω_f is the new rate of spin.
Thus, let's make it the subject to get;
ω_f = (I_i × ω_i/I_f)
Plugging in relevant values, we have;
ω_f = (I × 2.4/0.6I)
I will cancel out to give;
ω_f = 2.4/0.6
ω_f = 4 rev/s
Hello:
First, <u>the normal force</u> in y axis:
∑Fy = 0
∑Fy = N - Fy
∑Fy = N - 20 N * sen 37°
∑Fy = N = 12,87 N
Formula:
R = ma
F - F' = ma
F - (μN) = ma
20 N - (0.2 * 12,87 N) = 3 kg * a
20 N - 2.574 N = 3 kg * a
17,426 N / 3 kg = a
a = 5,8 m/s²
