Paper 2 mark scheme

Why, when a ball hits the ground, is energy transferred from the ball to the earth?

Velocity just after the bounce is less than just before the bounce

so the ball has lost energy

so loss of kinetic energy/reduced gpe

total energy of ball and earth is constant

Why does pressure on a swimmer increases as they diver further below the surface of the water?

Increasing depth increases the height/mass/volume above the swimmer

increasing the weight/force acting on the swimmer

Why does the velocity of a satellite change as it orbits the Earth?

Gravity causes the satellite to accelerate

the acceleration causes a change in direction

velocity changes because direction changes

Why does refraction happen at the boundary between deep and shallower water?

Velocity is slower in shallow water

so edge of wave entering shallow water slows down

but the part of the wave in deep water continues at a higher speed leading to a change in direction of the wave fronts

Why do wavefronts not refract at the boundary when they travel parallel to the boundary?

Every point on the wave enters the shallow water at the same time

so every point slows down at the same time

Why does the coil rotate continuously when there is a current in the coil in a simple electric motor?

The sides of the coil experience a force/current creates a magnetic field

The forces cause moments that act in the same direction/the magnetic fields interact causing the coil to rotate

the two halves of the commutator swap from one brush to the other

the commutator reverses the current so current in the same direction relative to magnetic field/forces in the same direction