You need to convert the 4 hr 7 min 29 s all to the same unit to start off with, the best thing to do usually is to convert to the smallest unit so we convert to seconds:
29s = 29s, no need to change anything there
7min = 7 X 60s = 420s
4h = 4 X 60min = 240min, 240 X 60s = 14,400s
Now that we've converted all the time units to the same unit (seconds), we add them together:
29 + 420 + 14,400 = 14,849s
Generally when we talk about speed and are using seconds as our unit for time, we express speed in m/s (metres per second), so now we convert the kilometres to metres:
1 km = 1000 m, so 42.2 km = 42.2 X 1000 = 42,200m
Finally, we can use our formula:
42,200 / 14,849 = 2.841942218 m/s
(I kind of rushed the calculations a little bit so that figure may not be 100% accurate, but the method is definitely correct)
Hope this helped :)
The question is incomplete! The complete question along with answer and explanation is provided below.
Question:
A 0.5 kg mass moves 40 centimeters up the incline shown in the figure below. The vertical height of the incline is 7 centimeters.
What is the change in the potential energy (in Joules) of the mass as it goes up the incline?
If a force of 1.0 N pulled up and parallel to the surface of the incline is required to raise the mass back to the top of the incline, how much work is done by that force?
Given Information:
Mass = m = 0.5 kg
Horizontal distance = d = 40 cm = 0.4 m
Vertical distance = h = 7 cm = 0.07 m
Normal force = Fn = 1 N
Required Information:
Potential energy = PE = ?
Work done = W = ?
Answer:
Potential energy = 0.343 Joules
Work done = 0.39 N.m
Explanation:
The potential energy is given by
PE = mgh
where m is the mass of the object, h is the vertical distance and g is the gravitational acceleration.
PE = 0.5*9.8*0.07
PE = 0.343 Joules
As you can see in the attached image
sinθ = opposite/hypotenuse
sinθ = 0.07/0.4
θ = sin⁻¹(0.07/0.4)
θ = 10.078°
The horizontal component of the normal force is given by
Fx = Fncos(θ)
Fx = 1*cos(10.078)
Fx = 0.984 N
Work done is given by
W = Fxd
where d is the horizontal distance
W = 0.984*0.4
W = 0.39 N.m
Within a single medium, the product of (wavelength) x (frequency)
is always the same number, for all waves. (It's the wave-speed.)
This means that longer wavelengths must have lower frequencies,
and shorter wavelengths must have higher frequencies, in order for
the product to always come out to be the same.