Transcript Do Now

• A car with a mass of 1,300 kg
is going straight ahead at a
speed of 30 m/sec (67 mph).
• The brakes can supply a force
of 9,500 N.
• Calculate:
a) The kinetic energy of
the car.
b) The distance it takes to
stop.
Calculate work
• A crane lifts a steel beam
with a mass of 1,500 kg.
• Calculate how much work is
done against gravity if the
beam is lifted 50 meters in
the air.
• How much time does it take
to lift the beam if the motor
of the crane can do 10,000
joules of work per second?
Given the force vs. displacement graph below for a
net force applied horizontally to an object of mass
100g initially at rest on a frictionless surface,
determine the object’s final speed when the net
force is 200 N. You may assume the force does not
change its direction.
In the following diagrams, a force F acts on a cart in motion on a
frictionless surface to change its velocity. The initial velocity of the
cart and final velocity of each cart are shown. You do not know
how far or in which direction the cart traveled. Rank the
magnitude of the work done by the force on each cart from
greatest to least.
A
2kg
2kg
B 3kg
3kg
V0=5m/s
C
5kg
V0=5m/s
V=2m/s
5kg
V=6m/s
V0=3m/s
D
4kg
V0=-1m/s
V=-3m/s
4kg
V=2m/s
A pitcher throws a 143-gram baseball toward the
catcher at 45 m/s. If the catcher’s hand moves back
a distance of 6 cm in stopping the ball, determine
the average force exerted on the catcher’s hand.
A chef pushes a 10-kg pastry cart from rest to a
distance of 5 meters with a constant horizontal
force of 10N. Assuming a frictionless surface,
determine the cart’s change in kinetic energy
and its final velocity.
A 2kg block sliding down a ramp from a height
3meters above the ground reaches the ground
with kinetic energy of 50 joules. Find the total
work done by the friction on the block as it
sliding down the ramp.