# Physics Year 11 Question Help (1 Viewer)

#### flowerp

##### Member
Hi, I would like help with the following question:

A car of mass 1500 kg is towing a trailer of mass 500 kg on level road.
i) What is the resultant force on the trailer when travelling at a steady speed of 60km/hr?
ii) What is the resultant force on the trailer when accelerating at 0.8 m/s^2?

Thank you!!!

#### Drdusk

##### sin(x) = tan(x) = x
i)
Remember the equation F = ma. Since the car & trailer is travelling at a constant speed 'a' must be zero. Which means the net resultant force is zero

ii) So we have a = 0.8. Just chuck that into F = ma, where m = 500kg as we need the resultant force on the trailer. This gives F = 400N.
However in most questions you would have friction, so you would've needed to balance the forces as so.

$\sum F_x = 400 - \mu_kmg \hspace{2mm} \text{where} \hspace{2mm} u_k \hspace{2mm}\text{is the coefficient of kinetic friction}$

#### flowerp

##### Member
i)
Remember the equation F = ma. Since the car & trailer is travelling at a constant speed 'a' must be zero. Which means the net resultant force is zero

ii) So we have a = 0.8. Just chuck that into F = ma, where m = 500kg as we need the resultant force on the trailer. This gives F = 400N.
However in most questions you would have friction, so you would've needed to balance the forces as so.

$\sum F_x = 400 - \mu_kmg \hspace{2mm} \text{where} \hspace{2mm} u_k \hspace{2mm}\text{is the coefficient of kinetic friction}$
Thank you very much !!!!!!!!!!