Answer:
Because the person is changing direction
Explanation:
The acceleration of an object is defined as the rate of change of velocity:
where
is the change in velocity
is the change in time
We must keep in mind that velocity is a vector, consisting of a speed and a direction. Therefore, a change in velocity means:
- either a change in the speed of the object, or
- a change in its direction
In this problem, the person is running around the track with a constant speed. However, his velocity is constantly changing (because the track is circular), this means that the change in velocity is not zero, and so there is a non-zero acceleration.
Answer:
The SI units of A, B and C are :
Explanation:
The position x, in meters, of an object is given by the equation:
Where
t is time in seconds
We know that the unit of x is meters, such that the units of A, Bt and must be meters. So,
So, the SI units of A, B and C are :
So, the correct option is (B).
Answer:
3099 J
Explanation:
The increase in thermal energy corresponds to the mechanical energy lost in the process.
The mechanical energy is given by the sum of gravitational potential energy and kinetic energy of the fireman:
At the top of the pole, the fireman has no kinetic energy, so all his mechanical energy is just potential energy:
When the fireman reaches the bottom, he has no gravitational potential energy, so his mechanical energy is just given by his kinetic energy:
So, the loss in mechanical energy was
and this corresponds to the increase in thermal energy.