(1) a car travelling at a constant speed of 20ms-1 overcomes a constant frictional resistance of 300N. What is the horse power of the engine? ( take 1h.p = 3/4 kw)
Recall;
Power = force x distance/time
also recall distance/time = velocity
also recall; Nm/s = Watts
Hence;
Power = 300N x 20m/s
Power = 6000Nm/s
Power = 6000watts or 6kw
Recall;
750watts = 1hp
but 1hp = 3/4kw
therefore;
1hp = 0.75kw
xhp = 6kw
Therefore;
0.75 * xhp = 6* 1
xhp = 6/0.75
xhp = 8hp
Corrected
Recall;
Power = force x distance/time
also recall distance/time = velocity
also recall; Nm/s = Watts
Hence;
Power = 300N x 20m/s
Power = 6000Nm/s
Power = 6000watts or 6kw
Recall;
750watts = 1hp
but 1hp = 3/4kw
therefore;
750watts = 3/4kw
0.75kw 3/4kw
0.75kw = 3/4kw
6kw = xhp
Therefore;
xhp = 3/4 x 6/0.75
xhp = 4.5/0.75
xhp = 6hp
It is correct
6000 Nm/s = 6 kw
M=f×s/t
To calculate the horsepower of the engine, we first need to calculate the work done by the engine against the frictional resistance.
The formula to calculate work is: work = force × distance.
In this case, the distance is not provided, but we know that the car is traveling at a constant speed of 20 m/s. Therefore, we can assume that the distance traveled is irrelevant for this specific calculation.
Now, we can calculate the work done by the engine against the frictional resistance:
work = force × distance
work = 300 N × distance
Since the distance is not given, we can assume it as 1 meter for simplicity:
work = 300 N × 1 m
work = 300 J (joules)
Next, we need to convert the work from joules to kilowatts since 1 horse power (h.p) is equal to 3/4 kilowatts (kW):
1 h.p = 3/4 kW
1 kW = 4/3 h.p
To convert joules (J) to kilowatts (kW), we divide the work by the time taken in seconds:
Power (kW) = work (J) / time (s)
Since the time is not given, we can assume it as 1 second:
Power (kW) = 300 J / 1 s
Power (kW) = 300 kW
Now, we can convert kilowatts to horse power:
Power (h.p) = 300 kW × (4/3) h.p/kW
Power (h.p) = 400 h.p
Therefore, the horse power of the engine is 400 h.p.