Projectile Motion
Identify a place/item where projectile motion is observed.
Ball rolling off desk
Parachute released from plane
etc
The period is the ________________
Time taken for an object/body to complete one revolution.
What is the SI unit for energy?
Joules
The letter (s) represents
displacement
The letter (g) represents
Gravitational force
A ball is free falling from a height of 40m. Take the acceleration due to gravity.
Calculate the velocity of the ball at the point of impact.
v = u + at
v = 0 + 9.8 x 2.9s
v = 28 m/s downwards
Complete the missing words;
Projectile motion occurs when an object travels in a C___________ path.
The speed remains CO__________
The velocity CH__________
Circular path
Constant
Changes
Calculate the torque
A bus driver applies a force of 45N on a steering wheel.
The radius of the wheel is 30cm. If the force is applied at 90° calculate the force on the steering wheel.
ꚍ = r ꓕ F
ꚍ = 0.3 x 45
= 13.5 N m clockwise.
Projectiles launched horizontally the velocity remains CONSTANT to its horizontal velocity.
TRUE/FALSE
True
A bus driver applies a force of 145N on a steering wheel.
The radius of the wheel is 40cm. If the force is applied at 90° calculate the torque on the steering wheel.
ꚍ = r ꓕ F
ꚍ = 0.4 x 145
= 58 N m clockwise.
A ball is hit horizontally from the top of a 40m high cliff with a velocity of 25 m/s to the right. Using an acceleration due to gravity and ignoring air resistance, calculate the following values.
The time it takes for the ball to land
s= ut + ½ at2
40= 0 + ½ 9.8t2
t = √40/4.9
t =2.86 s
Give the formula for Centripetal acceleration.
ac = v2/r
A toy car has a mass of 150g is released from a height of 1m. The car rolls down the track and travels inside the loop.
Calculate the potential energy.
PE = mgh
PE = 0.150 x 9.8 x 1
PE = 1.47 Joules
An athlete is swinging a ball of mass 7kg in a circular path. The ball is moving at 20m/s in a circle with a radius of 1.6m.
Calculate tensile (tension) in the wire.
Given the acceleration is 250 m/s/s
F = ma
F = ma
F = 7kg x 250m/s/s
F = 1.8 x 10^3 N
A wind turbine has blades 55m that rotate at a frequency of
20 revolutions per minute.
Calculate the frequency.
Frequency = rev/sec
= 20/60
= 0.33Hz
Fill in the missing words.
•Gravity is a D________ force so there is no force in the H__________ DIRECTION.
•The projectiles velocity D________ as it RISES.
•The projectile has UNIFORM velocity in the H__________ DIRECTION.
Downward force
Horizontal
Decreases
Horizontal
A wind turbine has blades 55m that rotate at a frequency of 20 revolutions per minute.
First calculate the period then the speed for the blade tips.
Period = 1/f
v = 2πr/T
Frequency = 0.33Hz
Period = 1/f
= 1/0.33
= 3 seconds
v = 2πr/T
v = 2x π x 55/ 3
= 115.2 m/s
Complete the sentence.
Torque occurs when there is a P_____point and a F_______ applied some DI_______ from the PIVOT point.
Pivot
Force
Distance
FN = Fnet - Fg
Fnet = 14.7N
Fg = - 1.47N (downward force)
FN = ?
Calculate FN
FN = 14.7 - (-1.47)
FN = 14.7+ 1.47
= 16.2N
An athlete is swinging a ball of mass 7kg in a circular path. The ball is moving at 20m/s in a circle with a radius of 1.6m.
a) Calculate the magnitude of the acceleration.
ac = v2 / r
ac = v2 / r
ac = 202 / 1.6
ac = 250 m/s/s
An athlete in a long jump leaps with a velocity of 7.5 m/s at an angle of 30 degrees to the horizontal.
What is the maximum height gained by the athlete given the maximum velocity is 6.5 m/s.
v2 = u2 + 2as
v2 = u2 + 2as
0 = 3.752 + 2 x 9.8 x s
s =3.752 / 2 x (9.8)
s = 71.7 cm
A wind turbine has 55m length blades which travel a distance of 150m in 2s.
First calculate the angle.
Ꝋ = distance/length
What angular velocity does the turbine rotate?
Ꙍ= ∆Ꝋ /t
Ꙍ= ∆Ꝋ /t
Ꝋ = distance/length
= 150/55
= 2.72 rad
= 2.72 x 180/π
= 156.3°
A mass 1500kg is released from a height of 1m. The mass rolls down the track.
E = 14 700 Joules
Calculate the speed as it reaches the bottom.
E = 1/2 mv2
E = ½ mv2
14700 = ½ 1500v2
14700 = 750v2
v = √14700/750 v = 4.43 m/s
A wind turbine has 60m length blades which travel a distance of 100m in 2s.
First calculate the angle.
What angular velocity does the turbine rotate?
Ꙍ= ∆Ꝋ /t
Ꝋ = distance/length
Ꙍ= ∆Ꝋ /t
Ꝋ = distance/length
= 100/60
= 1.67 rad
= 1.67 x 180/π = 95°
Fill in the missing words.
•A conical pendulum is a mass that travels in a horizontal direction on a ST________.
•A banked track is one where the track is inclined at some angle to the H____________.
•Banking tracks eliminate the need for FR__________ FORCE to turn.
•The speed at turns in banking tracks is known as D________ SPEED.
String
Horizontal
Frictional
Design