Physics 5054 · O Level · Balanced and unbalanced forces

Balanced and unbalanced forces — practice question

Aeroplanes travel at great heights, where the temperature is far below $0^\circ\text{C}$. Ice that builds up on an aeroplane may drop to the ground and hit the surface. Fig. 9.1 shows a block of ice dropping from an aeroplane as it nears an airport. The mass of the falling block of ice is 1.2 kg and the gravitational field strength $g$ is $10\,\text{N kg}^{-1}$.
(a)[1]

Calculate the weight of the ice block.

(b(i))[1]

As the block of ice falls, the air resistance force $F$ acting on it changes. State the value of $F$ at time $t=0$.

(b(ii))[1]

State the value of $F$ when $t=10.0\,\text{s}$.

(b(iii))[1]

Explain why the force $F$ changes.

(b(iv))[1]

State the energy change that occurs when the block is falling at terminal velocity.

(b(v))[3]

Using information from Fig. 9.2, determine the greatest kinetic energy of the block when it is falling to the ground at terminal velocity.

(c(i))[2]

The block hits the ground and comes to rest. This impact makes some of the ice melt. The specific latent heat of fusion of ice is $330\,\text{J g}^{-1}$. Calculate the largest possible mass of ice that melts as a result of the impact.

(c(ii))[2]

In reality, the mass of ice that melts on impact is smaller than the amount found in (c)(i). Suggest two reasons for this.

(d)[3]

As the solid ice melts, it becomes liquid water. Describe, in terms of molecules, how ice is different from liquid water.

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