Answers
Car going round a bend
a) Yes, it is moving in a circle so it must be
b) Towards the centre of the circle i.e. centripetally
c) F = mv2/r = 1500 x (25)2 / 50 = 18,750N
d) Friction between the tyres and the ground
e) If the road were wet or icy the car may continue in a straight line and end up in a field.
Car going over a hump
a) Its weight W and the normal contact force R from the road
b) The car is accelerating downwards so there must be a resultant vertical force. W > R
c) a = v2 / r = 122 / 25 = 5.76 m/s2
d) when mv2/r = mg so v2/r = g which occurs when v = 15.8 m/s
Ball on a string
a) The horizontal component of the tension in the string
b) Towards the centre of the horizontal circle described by the ball
c) The vertical component of the tension and the weight of the ball
d) i) The tension must increase as the acceleration is greater ii) The vertical component of the tension does not change as this is equal to the weight of the ball which is constant iii) This angle decreases ( but can never be zero! )
Satellites
a) The weight of the satellite towards the centre of the Earth
b) Resistive forces would slow down the satellite eventually causing it to crash back to Earth
c) a = v2 / r = (8000)2 / 6400,000 = 10 m/s2