help

[lilkrazyrae]

The acceleration of gravity near the surface of Mars is 3.72 m/sec2. If a rock is blasted straight up from the surface with an initial velocity of 85 m/sec, how high does it go?

I don't quite understand this one!!

 

[ChaoticLlama]

The object is propelled at 85 m/s, and so it reaches it's maximum height when velocity is 0 m/s

You have 3 given values and one unknown

a = -3.72 m/s²
V1 = 85 m/s
V2 = 0 m/s
D = ?

Plug in those 3 values into your kinematics equation and solve for D (which is distance in meters)

 

[Matt]

Hi lilkrazyrae,

Another way to do the problem is with conservation of energy.

All of the kinetic energy of the object transforms into potential energy once the object reaches its maximum height. Thus:

. . . .

Remember, g in this case is the gravitational acceleration at the surface of Mars, which is 3.72 m/s² (as opposed to the gravitational acceleration at the surface of the Earth, which is about 9.8 m/s²). Thus, the maximum height becomes:

. . . .

 

[lilkrazyrae]

thanks

thanks now i think i understand!