7 (a) Which of these is a vector? A distance B force C mass D work done figure 18 Calculate the value of W, the weight of child Q - Edexcel - GCSE Physics - Question 7 - 2023 - Paper 2

To calculate W, we start by using the principle of moments:

$ext{moment of W} = ext{moment of the weight of child P}$

Assuming we know the distance from the pivot to child P and the weight of child P, we can express this as:

$W imes d_W = W_P imes d_P$

Where:

• $W_P$ is the weight of child P
• $d_P$ is the distance from the pivot to child P
• $d_W$ is the distance from the pivot to child Q

Rearranging gives:

W = rac{W_P imes d_P}{d_W}

Using this equation and substituting the known values, we calculate W to 2 significant figures.

The crowbar acts as a lever, which is a simple machine that multiplies the force applied, making it easier to lift heavy objects.

Leverage Principle: When using a crowbar, the user applies a smaller force over a longer distance, resulting in a larger force being exerted at the other end where the heavy weight is located. This is due to the principle of moments, where the moments (force times distance) about the pivot must balance. Hence:

$ext{Force}_{ ext{applied}} imes ext{distance}_{ ext{to applied}} = ext{Weight} imes ext{distance}_{ ext{to pivot}}$

By increasing the distance from the pivot to where the force is applied, it allows a greater mechanical advantage, making it significantly easier to lift the heavy weight.