v
Unit for mass
kg
What is the unit for force?
N
What is the unit for time on the graphs
seconds (s)
What are the forms of mechanical energy?
Kinetic and gravitational potential energy
Definition for weight
It is the force exerted by gravity on an object
Define Newton's first Law
Newton's First Law states that an object at rest will remain at rest, and an object in motion will remain in motion at a constant velocity unless acted upon by a net external force
What shape line and where will you draw it for an object at rest on a distance time graph
straight horizontal line on zero
What is the unit for power
Watt
Definition for mass
A measure of the amount of matter in an object
Draw a freebody diagram of a car accelerating to the right
Vertical forces has to be equal length and touch the object. Labels - Fsupport for up and F gravity for down
Horizontal forces - one to the right larger than the one to the left - Label for right Fapplied and left Ffriction
What does the line look like for a car decelerating on a distance time graph
curved line with decreasing gradient
What is the formula for kinetic energy?
Ek = 1/2mv2
Calculate the speed of an object that travels 1.5 km in 20 minutes
v=d/t = 1500/(20x60) = 1.25 m/s
A car of mass 800kg is accelerating from 5m/s to 25 m/s for 1.2 s. Calculate the net force on the car.
a = (25 - 5)/1.2 = 16.7 m/s2
F = ma = 800 x 16.7 = 13 333.3 N
Draw a distance time graph for a car starting 0 accelerating for 100 m in 3s. It then travels at this speed for another 200m 4s. It now applies the brakes and stops the car in 4s while travelling 250 m.
A curve starting at 0 to 100 in 3s
A straight line from 100 - 300 m in 4s (7s)
A curve with a decreasing gradient to straight horizontal to 550m in another 4 s (11s)
A diver of 55 kg jumps of a 25m high dive board. Calculate the gravitational potential energy when he hits the water.
0J as all the gravitational potential energy changed into kinetic energy :)
A car is accelerating from rest to 20 m/s for 10 s. It then travels at 20 m/s for another 10 s. The driver sees a cat in the road and applies the brakes and stops the car in 5 s. Draw this graph in your book.
Straight line from 0 - 20 for 10 s (positive gradient
Horizontal line for 10 s. Zero gradient
Straight line for 5 s back to 0. negative gradient
A 1500kg car is accelerating at 4.3 m/s2 . The road friction is 140 N. Calculate the size of the force the engine gas to exert on the car to accelerate it at 4.3 m/s2
F = ma = 1500 x 4.3 = 6450N
F applied = Ffriction + Fnet = 6450 + 140 = 6590 N
A car is accelerating from rest to 20 m/s for 10 s. It then travels at 20 m/s for another 10 s. The driver sees a cat in the road and applies the brakes and stops the car in 5 s. Draw this graph in your book and use this graphs to calculate the total distance travelled by the car.
1/2 b h = 1/2 x 20 x 10 = 100m
bh = 20 x 10 = 200m
1/2 bh = 1/2 x 20 x 5 = 50 m
total distance 350 m
A diver of 55 kg jumps of a 25m high dive board. Calculate the speed when he hits the water.
Ep = Ek
55 x 10 x 25 = 1/2 x 55 x v2
v = 22.36 m/s