Increase the change in momentum of the collision
I think the correct answer from the choices listed above is option B. When calculating the power bill, power companies use kilowatt-hours. This unit is a derived unit of energy equal to 3.6 MJ. If energy is being transmitted or used at a constant rate (power) over a period of time, the total energy in kilowatt-hours is the product of the power in kilowatts and the time.
Hi there!
We can use the conservation of angular momentum to solve.
Recall the equation for angular momentum:
We can begin by writing out the scenario as a conservation of angular momentum:
= moment of inertia of the merry-go-round (kgm²)
= angular velocity of merry go round (rad/sec)
= final angular velocity of COMBINED objects (rad/sec)
= moment of inertia of boy (kgm²)
= angular velocity of the boy (rad/sec)
The only value not explicitly given is the moment of inertia of the boy.
Since he stands along the edge of the merry go round:
We are given that he jumps on the merry-go-round at a speed of 5 m/s. Use the following relation:
Plug in the given values:
Now, we must solve for the boy's moment of inertia:
Use the above equation for conservation of momentum:
Acceleration is a change in *speed* over time. In this case, the speed of the car increased by 90 km/hr in 6 s, giving it a rate of 90 km/hr/6s, or 15 km/hr/s. We’re asked for the acceleration in m/s^2, though, so we’ll need to do a few conversions to get our units straight.
There are 1000 m in 1 km, 60 min, or 60 * 60 = 3600 s in 1 hr, so we can change our rate to:
(15 x 1000)m/3600s/s, or (15 x 1000)m/3600 s^2
We can reduce this to:
(15 x 10)m/36 s^2 = 150 m/36 s^2
Which, dividing numerator and denominator by 36, gets us a final answer of roughly 4.17 m/s^2
