how far must you swim upstream to get directly in front of a pizza stand .2 km away on the other side of a river if you can swim 4km/hr and the river moves downstream at 1.5km/hr
Draw the diagram. You have a right triangle with the upstream leg = 1.5 and hypotenuse 4.
Thus, the distance across is √(4^1-1.5^2)=3.7
But you have to scale the triangle so the cross-stream distance is only 0.2, so the new upstream leg will be
0.2/3.7 * 1.5 = 0.08 km
The emf produced in a generator is Vemf=25sin377t. What is the frequency of rotation of the circular coil?
50Hz
60Hz
25Hz
15Hz
To answer this question, we need to understand the concept of relative velocity. Relative velocity is the combination of the velocities of two objects or entities observed from a particular reference point.
In this case, we have two velocities involved: the swimmer's velocity and the river's velocity. The swimmer's velocity is 4 km/hr, and the river's velocity is 1.5 km/hr downstream.
Now, we need to determine the effective velocity required to counteract the downstream movement of the river and reach the pizza stand directly in front of us.
To accomplish this, we subtract the river's velocity from the swimmer's velocity. In this case, 4 km/hr minus 1.5 km/hr gives us an effective velocity of 2.5 km/hr upstream relative to the pizza stand.
Since the distance to the pizza stand is 0.2 km, we can now calculate the time required to swim upstream using the formula Time = Distance / Velocity.
Time = 0.2 km / 2.5 km/hr
Time = 0.08 hours
Since 1 hour = 60 minutes, we can convert the time:
Time = 0.08 hours * 60 minutes/hour
Time = 4.8 minutes
Therefore, it would take approximately 4.8 minutes to swim upstream directly in front of the pizza stand that is 0.2 km away on the other side of the river, considering the given velocities.