Additional - Topic 2.3 and 2.4 - Motion and Forces Flashcards
The child and cart have a total mass of 50 kg. They travel at a velocity of 4 m/s.
Calculate the momentum of the child and cart.
momentum = ……………………………………………………………………… kg m/s
Substitution
50 x 4 (1)
Evaluation
200 (kg m/s) (1)
The father applies a steady force for a time of 1.5 s. The momentum of the
child and cart increases by 450 kg m/s.
Calculate the force which the father applies.
force = …………………………………………….. N
Substitution
450 / 1.5 (1)
Evaluation
300 (N) (1)
Momentum is a vector quantity.
State what is meant by a vector quantity.
An explanation to include
(quantity has) a size and a
direction
The rate of doing work is called ………………..
power
1
A javelin has a mass of 0.8 kg. In one throw, the javelin left the athlete’s hand at a
velocity of 25 m/s.
(i) Calculate the kinetic energy of the javelin as it left the athlete’s hand.
State the unit.
kinetic energy = ……………………………….. unit …………………
(ii) State the amount of work done by the athlete on the javelin to get it to a
velocity of 25 m/s.
work done = …………………………………………………..
i)
Substitution: ½ x0.8 x 252 (1) Evaluation 250 (1) 0.25 kJ scores 3 marks
ii)
250
The total mass of Joe, his heavy bag, and his bike is 55 kg.
Calculate the total weight.
Gravitational field strength, g = 10 N/kg
total weight = ………………………………………. N
550N
Andrew starts from the top of the hill and his speed increases as he goes
downhill.
He controls his speed and direction by using his skis.
He brings himself to a stop at the bottom of the hill.
Describe the energy changes that happen between starting and stopping.
Description including 3 of the following: • (Gravitational) potential energy (transferred) to KE(1) • Idea of energy transfer to heat/sound whilst descending (1) • Chemical energy is transferred to heat energy in Andrew (1) • Idea of energy dissipated on stopping (1)
Andrew returns to the top of the hill and starts again.
(i) His mass is 67 kg.
Show that his momentum is about 2000 kg m/s when his velocity is 31 m/s.
(ii) He falls over when his momentum is 2000 kg m/s.
After he falls over, he slows down by sliding across the snow.
It takes 2.3 s for his momentum to reduce to zero.
Calculate the average force on Andrew as he slows down.
i) substitution (1) 67 × 31 evaluation (1) 2077 (kg m/s)
ii) substitution (1) 2000 ÷ 2.3 evaluation (1) 870 (N)
The mass of the car is 625 kg.
Calculate the weight of the car.
gravitational field strength = 10N/kg
weight of car = …………………………………………………….. N
substitution 625x 10 (1) Evaluation 6250 (N) (1)
Use the words to complete the sentences.
balanced changing greater smaller zero
After a short time the ball falls at a steady speed.
The forces acting on the ball are now …………………………………………………….. .
The acceleration of the ball is now …………………………………………………….. .
After a short time the ball falls at a steady speed.
The forces acting on the ball are now balanced .
The acceleration of the ball is now zero .
The velocity of the aircraft when it lands is 75 m/s.
The mass of the aircraft is 130 000 kg.
Calculate the momentum of the aircraft.
momentum = ………………………………………………………………………………… kg m/s
substitution: (1)
130 000 × 75
evaluation: (1)
9 750 000 (kgm/s) (Ns)
When the aircraft lands, the momentum of each passenger also changes.
(i) Explain why it is more comfortable for a passenger if the aircraft takes a longer
time to slow down.
An explanation linking two of the following: • force is smaller/less (1) • momentum changes more slowly (1) • lower deceleration (1) • use of the formula (1)
Suggest why some aircraft need a very long runway to land safely.
Any two from: (for loaded aircraft) • has more mass (1) • has more momentum (1) • has more k.e. (1) • higher velocity • brakes need to do more work (1)
