AP Physics 1 Exam Question
A 2 kg block is sitting on a rough horizontal surface. The coefficient of kinetic friction between the block and the surface is 0.4. A horizontal force of 8 N is applied to the block, causing it to accelerate to the right. The acceleration of the block is measured to be 2 m/s².
Answer:
To find the net force acting on the block, we can use Newton's second law of motion, which states that the net force is equal to the mass of the object multiplied by its acceleration.
Applying this to the given situation:
Using the formula, net force (F_net) = m * a, we can calculate the net force:
F_net = 2 kg * 2 m/s² = 4 N
Therefore, the net force acting on the block is 4 N.
The frictional force (F_friction) acting on the block can be determined using the equation:
F_friction = coefficient of friction * normal force
Here, the coefficient of kinetic friction (μ_kinetic) is given as 0.4. We still need to find the normal force (N) to calculate the frictional force.
The normal force (N) is the force exerted by a surface to support the weight of an object resting on it. In this case, the weight of the block is balanced by the normal force.
Since the block is not sinking into the surface, the normal force will be equal to the weight of the block.
The weight (W) of the block is given by the formula:
W = m * g
Here, the mass of the block (m) is 2 kg, and the acceleration due to gravity (g) is approximately 9.8 m/s².
Therefore, W = 2 kg * 9.8 m/s² = 19.6 N
So, the normal force exerted on the block is 19.6 N.
Now, we can calculate the frictional force.
F_friction = μ_kinetic * N
F_friction = 0.4 * 19.6 N
F_friction = 7.84 N
Therefore, the frictional force acting on the block is 7.84 N.
In summary,