Twenty Questions Dynamics
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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
1. What is the unbalanced force?
• 15N – 7N• 8N right
15N7N
2. What force always acts in the opposite direction to motion?
• Friction.
3. Complete the table.
Planet Gravity (N/kg)
Mass of object (kg)
Weight of object (N)
Earth 10
Mars 4
9.8
10
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.
• The work done against gravity in raising an object.
6.What is Gravitational potential energy?
7. What formula denotes Electrical power?
• P = E/t
8. What are the units of energy?
• Joules.
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
21000kN
10. A ball rolls off a cliff, travelling at 3m/s. It hits the water below 5s later.
• 3m/s
What is it’s final horizontal speed?
11. A ball rolls off a cliff, travelling at 3m/s. It hits the water below 5s later.
• d = vt
• d = 3 x 5
• d = 15m
How far does the ball land from the base of the cliff?
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.
• v = u +at • v = 0 + 9.8(5) • v = 49ms-1
What is it’s final vertical velocity?
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?
• F = ma = 100(2) = 200N
• a =(v-u) = (20-0) = 2ms-2
t 10
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.
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