Thursday, 6 February 2014
Monday, 3 February 2014
Collisions
Collisions
1.
A truck of mass 2kg travels at 8
m/s towards a stationary truck of mass 6kg. After the collision they stuck
together and move off in the same direction. What is their common velocity?
2.
A car of mass 2000kg, traveling
at 10m/s, has a head on collision with a small sports car of mass 500kg. If
both cars stop dead on colliding, what was the velocity of the sports car
before the collision?
3.
A man wearing a bullet proof vest
stands on roller skates. His total mass is 80kg. A bullet of mass 20g is fired
at him at a speed of 400 m/s. If the bullet is stopped by the vest and falls to
the ground, what velocity will the man move at? How does your answer compare
with “the movies”?
Monday, 20 January 2014
Thursday, 9 January 2014
Monday, 6 January 2014
Monday, 9 December 2013
Assessed Homework
1. (a) points
plotted correctly;; [Deduct 1 mark
for each error] 2
[Line not necessary]
[Line not necessary]
(b) 3
(m/s); 1
(c) (i) acceleration = change in velocity / time taken; 1
[Accept a = (v-u)/t
[Accept a = (v-u)/t
(ii) acceleration
= 3/15 ; [Allow ecf from part (b)]
= 0.2 (m/s2); 2
= 0.2 (m/s2); 2
[6]
2. C
[1]
3. (i) acceleration (due to gravity) /
gravitational field strength 1
(ii) m
/ s2 or N / kg 1
[2]
4. (a) A description to include:
1. upward push/reaction/thrust;
2. of the ground on the athlete; 2
2. of the ground on the athlete; 2
(b) (i) A calculation to include:
1. acceleration = (v-u)/t
2. substitution of correct data,
3. = 9.7 m/s2; [Accept –9.7 m/s2] 3
2. substitution of correct data,
3. = 9.7 m/s2; [Accept –9.7 m/s2] 3
(ii) downwards;
negative gradient/backwards slope/athlete slowing down/retardation/
deceleration; 2
negative gradient/backwards slope/athlete slowing down/retardation/
deceleration; 2
(iii) A calculation to include:
1. F =
ma;
2. = 65 kg ´ 9.7 (m/s2);[Allow ecf from b(iii)]
3. = 630 – 633 (N);
[Accept either 65 ´ 10 m/s2 = 650 N for 2 marks
or 65 ´ 9.81 m/s2 = 638 N for 2 marks] 3
2. = 65 kg ´ 9.7 (m/s2);[Allow ecf from b(iii)]
3. = 630 – 633 (N);
[Accept either 65 ´ 10 m/s2 = 650 N for 2 marks
or 65 ´ 9.81 m/s2 = 638 N for 2 marks] 3
(iv) downward pull of the Earth/gravitational
pull;
[Reject gravity] 1
[Reject gravity] 1
[11]
5. (a) 15 (m/s) 1
(b) acceleration = change in speed ÷ time;
= 15 m/s ÷ 1.5 s;
= 10 m/s2; 3
= 15 m/s ÷ 1.5 s;
= 10 m/s2; 3
(c) (i) the acceleration decreases
(ii) this is shown by the decreasing slope/
gradient of the graph 2
(d) at
Pisa, air resistance affected the objects ;
the lighter object was affected more than the heavy one
there is no air on the Moon, so both objects had the same
acceleration/ neither object was affected by air resistance 3
the lighter object was affected more than the heavy one
there is no air on the Moon, so both objects had the same
acceleration/ neither object was affected by air resistance 3
[9]
6. (a) resultant/net/unbalanced force is in
forwards direction
/950>550 /driving force>resistive force/
forwards force is greater than backwards force; 1
/950>550 /driving force>resistive force/
forwards force is greater than backwards force; 1
(b) Ignore F = ma (or in words)
acceleration = force/mass;
= 400 (N) / 850 (kg);
= 0.47 (m/s2); 3
Bald 0.5 gains no marks
If acceleration = 1.12 (m/s2) award TWO marks maximum only
acceleration = force/mass;
= 400 (N) / 850 (kg);
= 0.47 (m/s2); 3
Bald 0.5 gains no marks
If acceleration = 1.12 (m/s2) award TWO marks maximum only
(c) the
driving force becomes zero; Accept decreases OWTTE;
the overall resistive force increases/braking force is added/air
resistance decreases;
plus 1 communication mark for ensuring that spelling,
punctuation and grammar are accurate, so that the meaning is clear; 3
the overall resistive force increases/braking force is added/air
resistance decreases;
plus 1 communication mark for ensuring that spelling,
punctuation and grammar are accurate, so that the meaning is clear; 3
[7]
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