- #1

Effitol840

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1) A freight train has a mass of [tex]1.1\times 10^7 kg[/tex]. If the locomotive can exert a constant pull of [tex]7.8\times 10^5 N[/tex], how long does it take to increase the speed of the train from rest to [tex]90 km/h[/tex]?

I figured I could just use the formula [tex]F=ma[/tex] to get the acceleration then I plugged that into [tex]v=at+v_0[/tex] to get the time. I came up with the answer of 1267.61. I might have a problem with units because [tex]a[/tex] was [tex]m/s^2[/tex] and [tex]v[/tex] was in [tex]km/h[/tex]. If that's the case how do I go about converting [tex]m/s^2[/tex] to [tex]km/h[/tex] or vice versa?

2) An elevator of mass m moving upward has two forces acting on it: the upward force of tension in the cable and the downward force due to gravity. Let the elevator have a mass of 1200 kg and an upward acceleration of 2.1 [tex]m/s^2[/tex]. Find [tex]T[/tex].

With this one I just plugged it into the equation [tex]T=ma[/tex] but I don't know if this is the correct equation. I got an answer of 2520[tex]N[/tex].

If anyone could help me with this please do.