topic 2

Question 1

another unit for g gravity?

A) j/kg
B) j/kg2
C) n/kg
D) n/kg2

Answer 1

C - n/kg

Question 2

two students try to determine a value for g, the acceleration due to gravity. measure time t for a small steel ball to fall through a height h from rest.

t = 0.74s
h = 2.50m

g = 2h / t^2

Answer 2

2 x 2.5 / 0.74^2

= 9.1

Question 3

explain how a more accurate value for g can be obtained

Answer 3

use an electronic timer to eliminate reaction time

Question 4

a car travelling at 15 m/s comes to rest in a distance of 14m when the breaks are applies

calculate deceleration with an equation from back
( a = (v^2) -u^2 / 2 x

Answer 4

= (-) 15^2 / 2 x 14

deceleration = 8.04 m/s^2

Question 5

student investigates relationship between force and acceleration (trolley investigation)

describe how the student could increase the accelerating force applied to the trolley

Answer 5

add weight or mass to the weight hanger

Question 6

student investigates relationship between force and acceleration (trolley investigation)

describe how the mass of the moving system can be kept constant

Answer 6

transfer mass between trolley and hanger

Question 7

explain how momentum is conserved in a collision (Q and R diagram) using newton’s third and second laws

Answer 7

momentum = mass x velocity
newton’s third law says action and reaction are equal and opposite so the force of k on q = -force of q on k. as well as this it also means change in momentum of Q = - change in momentum of R. this means that there is no overall change in momentum. in addition K accelerates because of the force from Q and there is a transfer in momentum between Q and K

Question 8

the object in figure 11 is moving in a circular path at a constant speed. explain why it isn’t moving with a constant velocity

Answer 8

velocity is a vector because direciton changes

Question 9

which of these is a vector?

A) energy
B) force
C) mass
D) work

Answer 9

B) force

Question 10

state the equation that relates acceleration to change in velocity and time taken

Answer 10

a = v - u / t

Question 11

a van accelerates from a velocity of 2m/s to a velocity of 20m/s in 12 s

calculate acceleration

Answer 11

20 - 2 / 12

18/12 = 1.5

Question 12

experiment with trolley and crumple zone.

explain how to carry out this investigation

Answer 12

measure the trolley masses and use f = m x a in finding the force. the velocity and impact time also needs to be measured. the experiment should be repeated with and without the spring as the crumple zone. times should be repeated and an average taken. in addition the starting point for the trolley should be the same every time with the same angle of slope and same release without pushing

Question 13

‘ the force exerted by the rocket on the asteroid is equal and opposite to the force exerted by the asteroid on the rocket ‘ explain how this statement links into the conservation of momentum in the collision

Answer 13

the time of collision is the same for both therefore momentum change is the same for both. equal and opposite forces mean an equal and opposite change in momentum. total momentum before a collision = total momentum after collision

Question 14

asteroid has a momentum of 7.5 x 10^10 kg m/s and a mass of 8.0 x 10^6 kg. calculate the speed of the asteroid

Answer 14

v = momentum change / mass

= 7.5 x 10^10 / 8.0 x 10^6

= 9.4 x 10^3

Question 15

calculate the distance the cyclist travels in 15s

Answer 15

distance = area under graph

= 1/2 x 7 x 15

= 52.5