forces

Question 1

Non-Contact Forces

Answer 1

A force which acts at a distance, without any contact between bodies, due to the action of a field

Question 2

what is the centre of mass?

Answer 2

the point through which the weight of an object act

Question 3

state Newtons
first law:
second law:
third law:

Answer 3

first: if resultant force 0, obj at rest if stationary, else moves at constant speed

sec: accel of obj is proportional to resultant force of obj, and inversely proportional to mass of obj. f=ma

third: when two obj interact, they exert equal and opposite forces on each other

Question 4

required practical measuring extension

Answer 4

-hang spring from a clamp and stand
-clamp a meter ruler alongside spring
-attach a mass hanger to the bottom of spring (100g)
-measure bottom of mass hanger when spring unstretched
-then measure hanger position when stretched
-Add another 100 g to the mass hanger
-Record the new mass and position from the ruler now that the spring has extended further
-Repeat this process until all masses have been added
-The masses are then removed and the entire process repeated again x 3 for average

Question 5

what is hooke’s law

Answer 5

The extension of an elastic object is directly proportional to the force applied, up to the limit of proportionality

Question 6

what is inertia

Answer 6

the tendency of an object to
continue in its state of rest or
motion

Question 7

typical weight of a car

Answer 7

1000 kg

Question 8

typical speed of a car

Answer 8

25m/s

Question 9

state law of conservation of momentum

Answer 9

total momentum before a collision is equal to total mom. after collision (in a closed system)

Question 10

what is a bearing

Answer 10

an angle measured clockwise from the north direction

Question 11

what happens when changing an objects momentum in order to avoid crash

Answer 11

-compressible material used
-in order to increase time taken for momentum to be lost
-and lower force

Question 12

how do protective pads help in collision

Answer 12

-(protective pads) increase the time taken to stop (during the collision)
-so the rate of change of momentum decreases
-reducing the force

Question 13

what is a moment

Answer 13

-a rotational or turning effect of a force

Question 14

levers transmit…

Answer 14

…the turning effect of a force

Question 15

gears transmit…

Answer 15

….turning effects

Question 16

typical braking distances for :
30 mph
60mph
70mph

Answer 16

-14m
-55m
-75m

Question 17

typical reaction times:

Answer 17

0.2 s - 0.9 s

Question 18

Plan an investigation to determine how the height of the ramp affects the acceleration
of the trolley.
[6 marks]

Answer 18

• 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
* 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

Question 19

A vehicle drives twice as fast.

What happens to the breaking distance?

Answer 19

If the vehicle speed increases by a factor of 2, then the breaking distance will increase by a factor 2 squared (2²), so 4 fold.

Question 20

what is terminal velocity

Answer 20

when an object falls in a constant velocity

Question 21

what is Newton’s second law

Answer 21

the size of the resultant force is directly proportional to the acceleration it causes

Question 22

what is inertia

Answer 22

the tendency for the motion of an object to remain unchanged

Question 23

upthrust is caused by

Answer 23

pressure on the bottom of the object being greater than on top of the object

Question 24

anything that gets dropped accelerates at:

Answer 24

9.8 m/s