Transcript Twenty Questions - Kelso High School

Twenty Questions
Dynamics
Twenty Questions
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
7N
15N
1. What is the unbalanced force?
• 15N – 7N
• 8N right
2. What force always acts in the
opposite direction to motion?
•
Friction.
3. Complete the table.
Planet
Gravity
(N/kg)
Mass of
object (kg)
Earth
9.8
10
Mars
4
10
Weight of
object (N)
98
40
4. Why does ½ mv2 = mgh?
•
Energy is always
conserved.
5. What is Kinetic energy?
• The energy an object
possesses due to it’s
motion.
6.What is Gravitational potential
energy?
• The work done against
gravity in raising an
object.
7. What formula denotes Electrical
power?
• P = E/t
8. What are the units of energy?
•
Joules.
21000kN
9. Calculate the acceleration of
the rocket as it takes off.
• Fun =ma
• a =Fun/m
• a =(21000000-7000000)
(7000000/9.8)
• a = 19.6ms-2
7000kN
10. A ball rolls off a cliff, travelling at
3m/s. It hits the water below 5s later.
What is it’s final horizontal speed?
• 3m/s
11. A ball rolls off a cliff, travelling at
3m/s. It hits the water below 5s later.
How far does the ball land from the
base of the cliff?
d
=
vt
•
d
=
3
x
5
•
d
=
15m
•
12. Give one situation in which friction
is increased.
• i) applying the brakes of
a car.
• ii) opening a parachute.
• iii) wearing rubber soled
shoes for rock climbing.
13. A ball rolls off a cliff, travelling at
3m/s. It hits the water below 5s later.
What is it’s final vertical velocity?
•
•
•
v = u +at
v = 0 + 9.8(5)
-1
v = 49ms
14. What is Newton’s first law of
motion?
• When balanced forces (or
no forces at all) act on an
object it remains at rest
or continue to move at a
steady speed in a straight
line unless acted upon by
an unbalanced force.
15. A 100kg man takes 10s to accelerate
to 20m/s from rest.
What force does he exert to do this?
• a =(v-u) = (20-0) =
t
10
• F = ma = 100(2) = 200N
-2
2ms
16. What is Newton’s second law of
motion?
•
Fun = ma
17. A tram takes 25s to gain 10kJ of
Potential energy.
How powerful is the tram’s motor?
• E =Pt
• P = E/t
• P = 10000/25
• P = 400W
18. Give one situation in which friction
is decreased.
• i) making racing cars
streamlined.
• ii) oiling moving parts in
a car engine.
• iii) using an air cushion
on an ‘air hockey’ table.
19. State the principle of conservation
of energy.
• During any energy
transformation the
total amount of energy
remains the same.
20. What does the formula Ew = Fd
represent?

The work done in
moving an object.