• dabouncerx24
In summary: For B, the weight of Sojourner on Mars is W=mg, so W=11.5*35.13=385.1 N. For C, the ramp must have a normal force of 32.96 N to support the vehicle.
dabouncerx24
Hi, I need a little help on a problem I did. I've most of the solutions but I think they're all wrong, can someone help me point out what I did wrong?

Here is the problem:

The Sojourner rover vehicle was used to explore the surface of Mars in 1997.
Here is some info to aid solving the below problems:

Mars data: Radius = 0.53 x Earth's R Mass = 0.11 x Earth's mass
Sojourner data: Mass = 11.5 kg Wheel diameter = 0.13 m Stored energy available: 5.4 x 10^5 J Power required for driving under avg. conditions: 10W
Land speed: 6.7 x 10^-3 m/s

a. Determine the acceleration due to gravity at the surface of Mars in terms of g, the acceleration due to gravity at the surface of Earth.

For a, I just used the same method that calculates the Earth's acceleration of gravity. I used:

g = G (m/r^2), with m and r being Mars' of course.
so it would be g = 6.67x10^-11 (6.567x10^23 / 1.1434x10^13), which gave me 3.05 m/s^2.

B. Calculate Sojourners weight on Mars.
I just used the W=mg concept. Sojourner is 11.5 kg and Mars' g is 3.05, so multiple and it = 35.13 N.

C. Assume that the vehicle is rolling down a ramp inclined at 20 degress to the horizontal. The ramp must be lightweight but strong enough to support the vehicle. Calculate minimum NORMAL force that must be supplied by the ramp.

What I did was I used the normal force equation.

so I got Normal F=mgcostheta = 11.5(3.05)(cos 20) = 32.96 N.

D. What is the net force on the vehicle as it travels across the Martian surface at constant velocity?

I kinda got stuck on this one so I made a guess. Since it is constant v, there is no acceleration. So according to the net force equation, F=ma, it becomes F=m(0), so there is no net force.

E. Determine the max distance that the vehicle can travel on a horizontal Martian surface using its stored energy.

I got completely stuck on this one, didn't do anyting for it.

Any help will be appreciated, thank you!

dabouncerx24 said:
Stored energy available: 5.4 x 10^5 J Power required for driving under avg. conditions: 10W
Land speed: 6.7 x 10^-3 m/s

E. Determine the max distance that the vehicle can travel on a horizontal Martian surface using its stored energy.

I got completely stuck on this one, didn't do anyting for it.

Any help will be appreciated, thank you!

I did not check your arithmetic, but your approach is correct for A-D. For E you have to use the information you were given in the probleam about power needed under "average" conditions. This means there is some force opposing the motion at all times. It could be due to a layer of sand or rolling friction. It does not matter what the source is. You just know that steady power has to be applied to keep the rover moving. Power is the rate of using energy, and your energy supply is limited.

For A, express mars' gravitation in terms of the Earths. aka

$$g_{mars} = \left(\frac{g_{mars}}{g_{earth}}\right) g_{earth}$$ where the quantity in brackest is numerical and the rest are just units.

## 1. How do I solve this physics problem?

Solving a physics problem involves breaking it down into smaller parts, identifying the relevant equations and principles, and applying them to find the solution. It also helps to draw diagrams and label all given values.

## 2. What if I don't understand the question or the given information?

If you are having trouble understanding the problem or the given information, try re-reading it and breaking it down into smaller parts. You can also consult your textbook or do some research online to gain a better understanding of the concepts involved.

## 3. Can I use a calculator to solve this problem?

Yes, a calculator can be a useful tool in solving physics problems. However, it is important to know when and how to use it correctly. Make sure to carefully input all values and double-check your calculations to avoid errors.

## 4. Do I need to show all my work when solving a physics problem?

Yes, it is important to show all your work when solving a physics problem. This not only helps you to check your own work, but it also allows others to understand your thought process and see where you may have made a mistake.

## 5. What if I can't find the solution or get the wrong answer?

If you are struggling to find the solution or getting the wrong answer, don't get discouraged. Physics problems can be challenging, and it may take some time and effort to solve them. Double-check your calculations and make sure you are using the correct equations and principles. You can also seek help from a teacher or tutor for further guidance.

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