Projectile Motion
Which of the following is an example of projectile motion
Running across a field
Free falling ball
Free falling ball
Give the formula for centripetal acceleration
ac = v2 /r
What is frequency?
The number of revolutions completed in a second.
Give the SI unit for magnetic flux
Weber (Wb)
Give the SI unit for weight.
Newton
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 given it takes 3 seconds for the ball to free fall.
v = u + at
v = 0 + 9.8 x 3
v = 28 m/s downwards
A toy car has a mass of 250g is released from a height of 3m. The car rolls down the track and travels inside the loop.
Calculate the potential energy.
E = 0.250 x 9.8 x 3
E = 7.35 Joules
Calculate the velocity given the radius is 1200 m and the period is 20 seconds.
v = 2πr/T
v = 2πr/T
v = 2π x 1200/20
Calculate the electric field given the voltage is 120V and the distance between the two plates is 5mm.
E = V/d
E = 120 /0.005
E = 24 000 V/m
Transformer 1 has 12kV and Transformer 2 has 1300V
Indicate if we have a step up or step down transformer.
Step down
A ball is allowed to free fall from a height of 30m on Mars. Take the acceleration due to gravity to be
g = 3.8 m/s/s.
Calculate the time taken for the ball to land.
s= ut + ½ at2
30= 0 + ½ 3.8t2
(square root (30/1.9) = t
t = 4 seconds
A toy car has a mass of 350g is released from a height of 1m. The car rolls down the track and travels inside the loop.
Calculate the kinetic energy given it has a velocity of 2m/s.
KE = 1/2 mv2
KE = 1/2 0.350 (2)2A wind turbine has blades 55m that rotate at 30 revolutions per minute.
Calculate the frequency.
Frequency = 30 / 60
Frequency = 0.5 Hz
Calculate the force acting on an electron within an electric field with a strength of 1200N.
F = qE
F = (-1.6 x 10^-19) (1200)
F =
Calculate the acceleration experienced by an electron travelling in a uniform electric field with a strength of 3.1 x 10^-5 N/C.
a = F/m
a = 3.2 x 10^-24 N/ 9.109 x 10^-31 kg
a = 3.5 x 10^6 m/s/s
A ball of mass 100g is hit horizontally from the top of a 30m high cliff with a velocity of 20 m/s to the right. Using an acceleration due to gravity and ignoring air resistance.
Given the time is 2.47 s. Calculate the velocity of the ball as it lands.
v= u + at
v= 0 + 9.8 x 2.47
v= 24.21 m/s
A toy car has a mass of 150g is released from a height of 2m. The car rolls down the track and travels inside the loop.
Calculate the speed as it reaches the bottom given it has 2.94 J of energy.
KE = 1/2 mv2
v = square root (2 x KE/ m)
v = square root (2 x 2.94/0.150)
v = square root (39.2)
v = 6.2 m/s
A wind turbine has 60 m length blades which travel a distance of 150m in 2s.
Calculate the angle.
Ꙍ= ∆Ꝋ /t
Ꝋ = distance/length
= 150/60
= 2.5 rad
= 2.72 x 180/pi
= 143°
A 10 m length of conductor carrying current (4A) is in a uniform magnetic field 600T.
The conductor is orientated at an angle of 45 degrees.
Calculate the force.
F = I x L x B Sin Ꝋ
F = 4 x 10 x 600 Sin 45
F = 16970 N
1.7 x 10^4 N
A motor lifts a mass of 500g. The motor has 300 turns in 0.3T magnetic field. If the the area 0.2m2 and the current 2A.
Calculate the torque.
Torque = nI BA Sin Ꝋ
Torque = 300 x 2 x 0.3 x 0.2 Sin 90
Torque =
An athlete in a long jump leaps with a velocity of 7.5 m/s at an angle of 40 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
0 = 3.752 + 2 x 9.8 x s
s =3.752 / 2 x (9.8)
s = 71.7 cm
A mechanic uses a 17 cm spanner to tighten a nut on a winch. He applies a force of 104N at an angle of 75° to the spanner.
Calculate the torque.
ꚍ = r F Sin Ꝋ
ꚍ = 0.17 x 104 Sin 75
= 17 N m perpendicular to the force arm
A wind turbine has 60 m length blades which travel a distance of 150m in 2s.
Calculate the angular velocity given the angle is 143o
Ꙍ= ∆Ꝋ /t
Ꙍ= ∆143 /2
Ꙍ=71o/s
A circular loop with a radius of 25cm is placed in a uniform magnetic field of 0.1T.
The coil is orientated at an angle of 40° to the magnetic field.
Calculate the torque acting on the loop which experiences 3A of current.
Area = πr 2
= 3.14 x 0.252
= 0.196
Torque = n x B x A Sin Ꝋ
Torque = 1 x 0.1 x 0.196 Sin 40
A rectangular wire loop is connected to DC. One side of the loop is next to the magnet. The loop is free to rotate.
If the side length closest to the magnet is 3.4m. Calculate to torque experienced by a 5kg mass.
T = F x d
T = mg x d
T = 5 x 9.8m/s/s x 3.4
T = 166.6 N/m