1.what force is needed to keep a 5 kg mass moving at a constant velocity of 10 ms -1 ? 2.calculate...
TRANSCRIPT
1. What force is needed to keep a 5 kg mass moving at a constant velocity of 10 ms-1?
2. Calculate the force needed to accelerate a 8 kg mass at 2 ms-2
3. Calculate the acceleration of the mass shown below.
Tutorials – 2 hours (expected)
Franky – Friday after schoolWill K – Friday after schoolJakob – Friday after schoolJacob – Friday after schoolWill S – Friday after schoolDavid – Friday lunch time (50 min)Sam – Sunday 10amScott – Sunday 10amTim –
Yesterday’s Lab… “Terminal Velocity”
• Do not expect any assistance or guidance from the teacher during the actual assessment
• Read the aim – this is the big picture (To find the relationship between…)
• Read thoroughly and follow every instruction very precisely
Yesterday’s Lab… “Terminal Velocity”
• Read, read, read… and read more
• Analysis – calculate the terminal velocity?
• Finish the lab write-up by Tomorrow
• Tutorial – Lunch time today
Examples of Forces• Thrust Force (an accelerating car)• Buoyancy Force (a floating ship)• Lift Force (a flying plane)• Tension Force (springs, ropes, BOTH ENDS)• Friction Force (against movement)• Weight Force (always downwards)• Support Force (usually upwards)
Can anything be moving without any force being applied on it?
• no force = stationary• no force = no acceleration
But how come Frankie is not moving or accelerating?
Because the “Net Force” is zero.Net force = the sum of all forces
Note: Net force is also known as Resultant force or Total force.
Net force = the sum of all forces, also called resultant force or total force.
Newton’s 1st Law:If the net force on an object is zero, the acceleration will be zero. Zero acceleration means the velocity of the object is constant.
Newton’s 2nd Law:If the net force on an object is NOT zero, the acceleration will NOT be zero. The relationship between Fnet and the acceleration is:
Fnet = ma (m = mass)
Both Fnet and a will always be in the same direction.
A tow truck pulls a car of mass 1250 kg with a force of 1500 N. The friction between the truck and the road is 600N.
a) Sketch a vector diagram to show the net force.
b) Calculate the car’s acceleration.
c) Once the car starts moving, what would happen if the two truck pulls with a smaller force of only 600N?
Q: What is your weight?Q: What is your mass?
Weight = MassWeight is a type of force,
measured in Newtons
Fw = mgg is the acceleration due to gravityg = 9.8 ms-2 everywhere on the surface of the Earth
A parachutist of mass 100 kg (including parachute) jumps from a great height. After a few seconds she reaches a terminal velocity of 50 ms-1.
a) What is the parachutist’s total weight?
b) What is the force of air resistance on her at terminal velocity?
The parachutist now pulls her ripcord and as her parachute unfurls she slows to a steady speed of 5.0 ms-1 in 2.0 seconds.a) Calculate the acceleration over the
2 seconds.b) Calculate the net force acting on
her over the 2 seconds.c) What is the force of air resistance
now?
Newton’s 3rd Law:For every action force there is an equal and opposite reaction force. (eg. a gun recoil)