Past Paper

• Mass

• Velocity

• momentum before = momentum after

• Before diving in the momentum of the diver and boat is zero

• After diving the diver has forwards momentum

• Therefore the boat has equal backwards momentum

Explain what would happen to the motion of the boat if there were more people on the boat when the swimmer dived off

• The boat moves back more slowly

• because there is more mass (but momentum stays the same)

• As she swims there is a drag force

• As speed increases so does the drag force

• She accelerates less

• Drag force = thrust force or resultant force is zero

• The swimmer reaches terminal velocity

Explain what would happen to a spring if the student kept adding weights?

• The spring will be deformed

• Because it has passed the elastic limit

• Momentum before (collision) = momentum after (collision

• Momentum of skater A decreases and momentum of skater B increases

• Velocity of skater A decreases and velocity of Skater B increases

• D

• Needs the greatest force to extend the spring the same amount

Describe the relationships shown in Figure 9. You should include factors that would affect the gradient of the lines (6 marks)

• Use of drugs, alcohol, tiredness and distractions would increase the thinking distance

• Thinking distance increases with speed

• Thinking distance is directly proportional to speed

• Use of drugs, alcohol, tiredness and distractions would increase the gradient of thinking distance

• Poor brakes, poor tyres, wet / icy roads and mass would increase the braking distance

• Braking distance increases with speed

• Braking distance increases at an increasing rate (with speed)

• Poor brakes, poor tyres, wet/icy roads and mass would increase the gradient of braking distance

• Braking distance is directly proportional to speed squared

• Stopping distance = thinking distance + braking distance •

• Factors that increase thinking and / or braking distance would increase the gradient of stopping distance

• 7.1 Constant velocity

• 7.2 The man will accelerate, so force B increases, until force B equals force A, the man moves at a higher constant velocity

• Velocity

• Mass

• Total momentum is zero after the collision (because the bumper cars are stationary)

• Because the momentum of each car before the collision was equal (in magnitude) and opposite (in direction)

• So the total momentum of the bumper cars was zero before the collision

• and momentum is conserved

• Springs with a low spring constant

• Because they can compress by a larger amount (for a given force)

• Thrust decreases so there is a resultant force in opposite direction

• Lift must decrease (because weight stays the same) so there is a resultant downwards force

Measurements:

• Place one wooden block under the ramp

• Vary the height by placing a different number of wooden blocks

• Measure the height of the ramp using a metre rule

• Measure the distance travelled using a metre rule

• Measure time taken using light gates (and computer/datalogger)

• Measure time taken using a stopclock or ticker timer

• Release trolley from the same position each time

• Release the trolley without applying a force results

Results:

• Repeat at the same height and calculate a mean

• Repeat for different heights

• Calculate acceleration using a = (v-u)/t or a = v²- u² / 2s

• 4.1 Scalar quantity has magnitude and no direction, vector quantity has magnitude and direction

• 4.2 Resistive force acts on the ball, so (resultant) force in opposite direction to velocity

• Momentum is conserved in the collision (assuming no external forces)

• Momentum of the pin increases

• Therefore the momentum of the ball must decrease

• Same maximum force applied by the brakes

• Because mass is less there is a greater deceleration

• Braking distance is less

• At maximum power the forward force of the engines is constant

• As it accelerates the air resistance increases

• Resultant force = force from engines – air resistance

• Therefore resultant force decreases

• Acceleration is directly proportional to resultant force

A train collides with a stationary carriage on a track.

Explain why the velocity of the train after the collision is less than it was before the collision. Use ideas about momentum in your answer

• Total momentum is conserved in the collision

• During the collision the momentum of carriage increases

• So the momentum of train decrease

• Since mass (of train) is constant, velocity (of train) decreases

Describe a method the student could use

• Clamp a pulley onto the edge of the desk

• Attach a string to the trolley and place the string over the pulley

• Attach a mass holder to the string

• Place a slotted mass on the mass holder

• Use W = mg to calculate the force

• Mark the starting and finishing points of the trolley on the runway

• Measure the distance between the two marks with a metre rule

• Time how long it takes to travel between the two marks with a stopclock / timer

• Use v = s / t and a = Δv / t

Describe what is meant by ‘inelastically deformed’

• Will not go back to its original length

• When the force is removed

Explain why large decelerations may be dangerous

• The brakes can overheat

• (so) the brakes will not work properly

• Drag is greater than weight

• (so) there is a resultant force acting in the opposite direction to the velocity (causing deceleration)

• As velocity decreases the drag decreases

• (until) drag is equal to weight (so velocity is constant)

• (as a spring decompresses) the spring exerts a force on the gymnast

• (so) work is done on the gymnast

• measure the original length of the spring and the compressed length of the spring (using a metre rule)

• compression = original length − compressed length

• Parachutes increase the effective area

• (so) there is the same air resistance at a lower speed

• (so) resultant force is zero at a lower speed (with the parachutes open)

Thinking distance:

• Condition of brakes and tyres does not affect thinking distance

• Speed does not affect thinking / reaction time

• Decreased speed decreases thinking distance

Braking distance:

• Condition of tyres affects friction between tyres and road

• Poor condition of tyres and brakes increases braking distance

• Decreased speed decreases braking distance

Safety:

• Stopping distance = thinking distance + braking distance

• Poor condition of brakes and tyres increases stopping distance

• Decreased speed decreases stopping distance

• Decreased speed decreases the chance of the driver losing control of the vehicle

• Decreased speed decreases the chance of a collision

• Decreased speed decreases the risk of injury during a collision

• Frictional / braking force is greater (for the faster car)

• (so) more work done

• (so) the risk of the brakes overheating is greater