P5 - FORCES

Question 1

What is a contact force?

Answer 1

When objects physically touch.
E.g, friction, air resistance and tension.

Question 2

What is a non-contact force?

Answer 2

When objects are not touching.
E.g, magnetism, electrostatic force and gravity

Question 3

What is a scalar quantity?

Answer 3

A quantity that only has magnitude

Question 4

What is a vector quantity?

Answer 4

A quantity that has magnitude and direction

Question 5

How do we find the resultant vector?

Answer 5

Adding the two numbers together on a diagram.
If at right angles = Pythagoras is used or trigonometry.

Question 6

What does it mean if there’s no resultant force?

Answer 6

No resultant force = no acceleration.

Question 7

Name some similar scalar and vector quantities

Answer 7

Distance (Scalar), Displacement (Vector)
Speed (Scalar), Velocity (Vector)

Question 8

What is WEIGHT?

Answer 8

Weight is the force that gravity pulls an object down with.

Question 9

What is the equation for weight?

Answer 9

Weight = mass x gravitational field strength #
W=mg

UNITS; weight (N), mass (kg), gfs (N/kg)

Question 10

What is WORK DONE?

Answer 10

‘energy transferred by a force’.

Question 11

What is the equation for work done?

Answer 11

work done = force x distance
W=fd

UNITS; work done (J), Force (N), Distance (M)

Question 12

What is HOOKE’S LAW?

Answer 12

Force and extension and directly proportional.
>Any objects that deforms elastically obeys this law.

Question 13

What is the equation for force?

Answer 13

Force = spring constant x extension
F=ke

UNITS; force (N), spring constant (N/m), extension (m)

Question 14

Describe the practical for Hooke’s law

Answer 14

-Secure a clamp to a bench using a G-clamp.
-Use bosses to attach two clamps to the clamp stand.
-Attach the spring to the top clamp, and a ruler to the bottom clamp.
-Adjust the ruler so that it is vertical, and with its zero level with the top of the spring.
-Hang a 100g slotted mass carrier from the spring. Measure and record the new length of the spring.
-Add a 100g slotted mass to the carrier. Measure and record new length of the spring.
-Repeat step 7 until a total of 1000g has been added.

Question 15

Newton’s Equations Of Motion

Answer 15

SUVAT
S- displacement (m)
U- initial velocity (m/s)
V- final velocity (m/s)
A- acceleration (m/s^2)
T- time (s)

Question 16

What is the initial velocity if something is at rest + final velocity if something stops?

Answer 16

If starting at rest, u=0m/s
If stopping, v=0m/s

Question 17

What is Newton’s 1st law?

Answer 17

No resultant force acts on an object, its motion will be constant (velocity will not change).

Question 18

What is Newton’s 2nd law?

Answer 18

F=ma (force = mass x acceleration)

Question 19

Describe the practical for investigating the effect of force on acceleration

Answer 19

-Use the metre ruler to measure out intervals on the bench. Draw straight lines with pencil or chalk across the table at these intervals.
-Attach the bench pulley to the end of the bench.
-Tie some string to the trolley. Pass the string over the pulley and attach the mass hanger to the other end of the string.
-Make sure the string is horizontal and is line with the trolley.
-Hold the trolley at the starting point.
-Attach the full set of weights to the end of the string.
-Release the trolley at the same time as the stopwatch is pressed. (Lap mode at each measured interval on the bench). Final time is at 1.0m.
-Record the results in a table and repeat step 7 to calculate an average time for each interval.
-Repeat steps 5-8 for decreasing weights on the weight hanger.

Question 20

What is Newton’s 3rd law?

Answer 20

For every action (force), there is an equal and opposite reaction (force).

Question 21

How do you work out the stopping distance of a car?

Answer 21

Thinking distance + braking distance

Question 22

What can thinking distance be affected by?

Answer 22

-speed
-distractions
-drugs
-alcohol
-tiredness

Question 23

What can braking distance be affected by?

Answer 23

-condition of brakes/tyres
-road conditions#
-weather conditions

Question 24

What is the equation for momentum?

Answer 24

momentum = mass x velocity
m=mv

UNITS; momentum (kgm/s), mass (kg), velocity (m/s)

Question 25

What happens to momentum during a collision?

Answer 25

In any collision, total momentum is ALWAYS conserved.

rebound: m1u1 = m1u1 + m2u2 (if there’s a second object)
coupling: m1u1 = mv
recoil: 0 = m1v1 + m2v2