Download Force and Drag 1. Define the newton

Force and Drag
1.
Define the newton.
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[Total 1 mark]
2.
State why the equation ‘F = ma’ cannot be applied to particles travelling at speeds very close to
the speed of light.
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[Total 1 mark]
3.
The figure below shows the horizontal forces acting on a car of mass 900 kg when it is travelling
at a particular velocity on a level road.
The total forward force between the tyres and the road is 200 N and the air resistance (drag) is
80 N.
(i)
Calculate the acceleration of the car.
acceleration = ................................................ m s–2
[2]
(ii)
Explain why we cannot use the equation v = u + at to predict the velocity of the car at a
later time even when the forward force is constant.
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[1]
[Total 3 marks]
4.
The figure below shows a person being lifted vertically upwards by a rope.
T
rope
The mass of the person is 72 kg. The upward vertical acceleration of the person is
1.4 m s–2.
Calculate the tension T in the rope.
T = ...................................................... N
[Total 3 marks]
.
A skydiver jumps from a stationary hot-air balloon several kilometres above the ground.
(a)
In terms of acceleration and forces, explain the motion of the skydiver
immediately after jumping ...............................................................................
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at a time before terminal velocity is reached ...................................................
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at terminal velocity. ..........................................................................................
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[6]
(c)
The figure below shows a sketch graph of the variation of the velocity v of the skydiver
with time t.
v / m s-1
50
25
0
0
10
20
30
t/s
Suggest the changes to the graph of the figure above, if any, for a more massive (heavier)
skydiver of the same shape.
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[2]
[Total 8 marks]
6.
The figure below shows a wooden block motionless on an inclined ramp.
block

W
ramp
The angle between the ramp and the horizontal is θ.
(i)
The weight W of the block is already shown on the figure. Complete the diagram by
showing the normal contact (reaction) force N and the frictional force F acting on the block
[2]
(ii)
Write an equation to show how F is related to W and θ.
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[1]
[Total 3 marks]
7.
The figure below shows a gannet hovering above a water surface.
gannet
30m
water
6.0m
fish
The gannet is 30 m above the water. It folds in its wings and falls vertically in order to catch a
fish that is 6.0 m below the surface.
Ignore air resistance.
(a)
Calculate
(i)
the speed that the bird enters the water
Speed = .............................. m s–1
[2]
(ii)
the time taken for the bird to fall to the water surface.
time = ........................................ s
[2]
(b)
The bird does not continue to travel at the acceleration of free fall when it enters the
water. State and explain the effect of the forces acting on the bird as it falls
(i)
through the air
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[2]
(ii)
through the water.
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[2]
[Total 8 marks]