# Tutor profile: Caleb V.

## Questions

### Subject: Chemistry

Which is the rarest element in the universe?

Astastine is the rarest naturally occurring element in the world, with only 25 grams on the earth at any given time!

### Subject: Anatomy

Why is calcium an extremely important ion for skeletal muscle contraction?

Calcium is normally stored in the sarcoplasmic reticulum. When the action potential signaling the skeletal muscle contraction reaches the muscle, calcium is released from the sarcoplasmic reticulum and binds the tropomyosin. This allows the myosin to bind to the actin head, which initiates the cross-bridge cycling, and the two protein components pull together. This happens along every sarcomere across the muscle which allows for a skeletal muscle contraction. Now imagine this happening every time you use your skeletal muscles, this must be hundreds of thousand contractions a day!

### Subject: Physics

A car accelerates from rest at 10m/s^2. What is the velocity of the car after 6 seconds?

We know that acceleration (a) is equal to final velocity (Vf) minus initial velocity (Vi), divided by time (t). From the questions, we can gather that a = 10m/s^2, Vi = 0 m/s, time is equal to 6 seconds. We are looking for the final velocity of the car, so Vf. To plug it in. a = (Vf-Vi)/t. 10 = (Vf - 0) / 6. MULTIPLY each side by 6. 60= Vf-0. ADD 0. 60 = Vf. The final velocity of the car is 60 m/s. To put that into perspective, 60 m/s = 134 mi/hr, so we are dealing with a very fast car.