Question

a team of worthy sled dogs pull their 60 kg sled along a flat surface at a constant velocity with a force of 1500 n. select all of the statements that are true about this interaction. neglect frictional effects caused by air resistance. (select more than one)
a the net force acting on the sled is 1500 n.
b there is no net force acting on the sled.
c the sled will accelerate as the dogs continue to pull with 1500 n.
d the tensional force in the rope that connects the harness to the sled is 750 n.
e the frictional force between the sled skis and the snow is 1500 n.

Explanation:

Step1: Analyze the motion of the sled

Since the sled is moving at a constant velocity, according to Newton's first law of motion, the net force acting on an object in equilibrium (constant - velocity motion) is zero.

Step2: Analyze each option

• Option A:

If the net force were \(F_{net}=1500\ N\), the sled would be accelerating (by \(F = ma\)). But since \(v=\text{constant}\), \(a = 0\) and \(F_{net}=0\). So, option A is wrong.

• Option B:

When an object moves at a constant velocity (\(a = 0\)), from \(F_{net}=ma\) (Newton's second law, where \(m\) is the mass of the object and \(a\) is the acceleration), and since \(a = 0\), \(F_{net}=0\). So, option B is correct.

• Option C:

Acceleration \(a=\frac{F_{net}}{m}\). Since \(F_{net} = 0\) (because \(v=\text{constant}\)), \(a = 0\). The sled will not accelerate. So, option C is wrong.

• Option D:

There is no information given to split the \(1500\ N\) force into two - equal parts. The problem only states that the dogs pull with a force of \(1500\ N\). If we assume the rope is massless and inextensible and the force applied by the dogs is \(1500\ N\), the tension in the rope (which transmits the force from the dogs to the sled) is \(1500\ N\). So, option D is wrong.

• Option E:

Since \(F_{net}=F_{applied}-F_f=0\) (because \(a = 0\) and \(F_{net}=ma\)), and \(F_{applied}=1500\ N\), then \(F_f = 1500\ N\) (frictional force opposes the applied force). So, option E is correct.

Answer:

B. There is no net force acting on the sled; E. The frictional force between the sled skis and the snow is \(1500\ N\)