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(II) The forearm in Fig. 8–46 accelerates a 3.6-kg ball at 7.0 m/s2 by means of the
Chapter 8, Problem 38P(choose chapter or problem)
(II) The forearm in Fig. 8–46 accelerates a 3.6-kg ball at 7.0 m/s2 by means of the triceps muscle, as shown. Calculate (a) the torque needed, and (b) the force that must be exerted by the triceps muscle. Ignore the mass of the arm.
Questions & Answers
QUESTION:
(II) The forearm in Fig. 8–46 accelerates a 3.6-kg ball at 7.0 m/s2 by means of the triceps muscle, as shown. Calculate (a) the torque needed, and (b) the force that must be exerted by the triceps muscle. Ignore the mass of the arm.
ANSWER:
Solution 38P:
Step 1 of 2:-
Here we have to find the torque needed and the force exerted by the triceps muscle.
We know that, when there is a net torque on the system, it causes angular acceleration and the angular momentum is no more conserved.
Here we have assumed that the arm is massless.
The torque can be written as:
Where I is the moment of inertia.
is the angular acceleration.
So,
.
Here we have used the relationship between angular and tangential acceleration, which is: .
The position vector is: .
The mass is: .
The tangential acceleration is: .
So, the torque will be,
So, the required torque is: 7.812 Nm.