# Rotational Kinematics Question Homework Help needed

• rmarkatos
In summary, the sun rotates in a circular orbit around the center of the Milky Way Galaxy with a radius of 2.2x10^20 m and an angular speed of 1.2x10^-15 rad/s. To calculate its tangential speed, the formula VT=r(w) is used. For part (b), the constant speed of 1.2x10^-15 rad/s and the fact that one revolution is equal to 2(pi) radians can be used to calculate the time it takes for the sun to make one revolution using the formula w(omega)= 0(theta)/t(time).

#### rmarkatos

Our sun rotates in a circular orbit about the center of the Milky Way Galaxy. The radius of the orbit is 2.2x10^20 m, and the angular speed of the sun is 1.2x10^-15 rad/s. (a) What is the tangential speed of the sun? (b) How long (in years) does it take for the sun to make one revolution around the center?

(a) for part a all i did was VT=r(w) w=omega

(b) for this part since we know the constant speed is 1.2x10^-15 rad/s and since its one revolution theta should equal 2(pi) radians so am i supposed to use w(omega)= 0(theta)/t(time)

is this correct?

thanks for the help everyone.......

Yes, your approach is correct. To find the tangential speed, you can use the formula VT = rω, where VT is the tangential speed, r is the radius of the orbit, and ω is the angular speed. Plugging in the values given, we get VT = (2.2x10^20 m)(1.2x10^-15 rad/s) = 2.64x10^5 m/s. This is the speed at which the sun is moving tangentially around the center of the Milky Way Galaxy.

For part (b), we can use the formula ω = θ/t, where ω is the angular speed, θ is the angle of rotation, and t is the time taken. As you correctly stated, for one revolution, θ = 2π radians. So, we can rearrange the formula to get t = θ/ω = (2π rad)/(1.2x10^-15 rad/s) = 5.24x10^15 seconds. To convert this to years, we can divide by the number of seconds in a year, which is approximately 3.15x10^7 seconds. This gives us the time taken for one revolution as approximately 166 billion years. This is a very long time, considering the current estimated age of the universe is around 13.8 billion years.

## 1. What is rotational kinematics?

Rotational kinematics is the branch of physics that studies the motion of objects in a circular or rotational motion. It involves concepts such as angular velocity, angular acceleration, and torque.

## 2. How do you calculate angular velocity?

Angular velocity is calculated by dividing the change in angular displacement by the change in time. It is represented by the symbol ω and its unit is radians per second (rad/s).

## 3. What is the difference between angular velocity and linear velocity?

Angular velocity refers to the rate at which an object rotates or revolves around a fixed axis, while linear velocity refers to the rate at which an object moves in a straight line. Angular velocity is measured in radians per second, while linear velocity is measured in meters per second.

## 4. How does rotational kinematics relate to everyday life?

Rotational kinematics plays a significant role in many everyday activities, such as riding a bike, driving a car, or throwing a ball. It also helps explain the motion of objects such as wheels, gears, and satellites.

## 5. What are the key equations used in rotational kinematics?

Some of the key equations used in rotational kinematics include ω = Δθ/Δt (angular velocity), α = Δω/Δt (angular acceleration), and τ = Iα (torque), where ω is angular velocity, Δθ is angular displacement, Δt is time, α is angular acceleration, τ is torque, and I is the moment of inertia.