Question

a 20kg wagon is pulled along a level ground by a rope inclined at 30 degrees above the horizontal.a friction force of 30 newtons opposes the motion.how large is the pulling force of the wagon is movin at constant speed

Answer 1

a 20kg wagon is pulled along a level ground by a rope inclined at 30 degrees above the horizontal. A friction force of 30 newtons opposes the motion. How large is the pulling force of the wagon is moving at constant speed

$$\alpha = 30{}^{\circ}$$ $$mg = 9.8 \cdot \frac{m}{s^2} \cdot 20kg = 196N$$ $$F_{fr} = 30 - \text{force of friction}$$ $$F - \text{force of pulling}$$

From Newton's first law of motion:

If there is no net force on an object, then its velocity is constant.

So, vector sum of forces equals 0.

Therefore:

$$F_{fr} + m \cdot g \cdot \sin \alpha = F$$ $$F = 30N + 20kg \cdot 9.8 \frac{m}{s^2} \cdot \sin 30{}^{\circ} = 30N + 20kg \cdot 9.8 \frac{m}{s^2} \cdot \frac{1}{2} = 128N$$

Answer:

The pulling force of the wagon is $F = 128N$