Maia is at a skatepark. She stands on her skateboard as it rolls in a straight line down a gentle slope at a constant speed of 3.0 m s\(^{-1}\), as shown in Figure 8. The slope is 5° to the horizontal. The combined mass of Maia and the skateboard is 65 kg. --- 0 WORK AREA LINES (style=lined) --- --- 5 WORK AREA LINES (style=lined) --- Near the bottom of the ramp, Maia takes hold of a large pole and comes to a complete rest while still standing on the skateboard. Maia and the skateboard now have no momentum or kinetic energy. --- 3 WORK AREA LINES (style=lined) --- a. b. 55.5 N c. Momentum: → Maia and the skateboards momentum was transferred into the pole and hence into the Earth. Due to the Earth’s very large mass, the effect on its velocity is negligible. Kinetic energy: → The kinetic energy of Maia and the skateboard would have been transformed into heat energy between the contact of Maia and the pole and/or transferred into the work done by Maia’s muscles in slowing herself down. a. b. Total frictional forces: → Constant speed means that the force down the slope of the incline is equal to the sum of the frictional forces acting on Maia and the skateboard. c. Momentum: → Maia and the skateboards momentum was transferred into the pole and hence into the Earth. Due to the Earth’s very large mass, the effect on its velocity is negligible. Kinetic energy: → The kinetic energy of Maia and the skateboard would have been transformed into heat energy between the contact of Maia and the pole and/or transferred into the work done by Maia’s muscles in slowing herself down.
\(F_{\text{down slope}}\)
\(=F_f\)
\(=mg\, \sin\, \theta\)
\(=65 \times 9.8 \times \sin\,5^{\circ}\)
\(=55.5\ \text{N}\)
PHYSICS, M2 2018 VCE 8-9 MC
A railway truck \(\text{X}\) of mass 10 tonnes, moving at 6.0 m s\(^{-1}\), collides with a stationary railway truck \(\text{Y}\) of mass 5.0 tonnes. After the collision the trucks are joined together and move off as one. The situation is shown below.
\(\text{Question 8}\)
The final speed of the joined railway trucks after the collision is closest to
- \( 2.0 \text{ m s}^{-1}\)
- \( 3.0 \text{ m s} ^{-1}\)
- \( 4.0 \text{ m s} ^{-1}\)
- \( 6.0 \text{ m s} ^{-1}\)
\(\text{Question 9}\)
The collision of the railway trucks is best described as one where
- kinetic energy is conserved but momentum is not conserved.
- kinetic energy is not conserved but momentum is conserved.
- neither kinetic energy nor momentum is conserved.
- both kinetic energy and momentum are conserved.
PHYSICS, M2 2019 VCE 20 MC
As part of their Physics course, Anna, Bianca, Chris and Danshirou investigate the physics of car crashes. On an internet site that describes what happens during car crashes, they find the following statement.
"It happens in a flash: your car goes from driving to impacting ... As the vehicle crashes into something, it stops or slows very abruptly, and at the point of impact the car's structure will bend or break. That crumpling action works to absorb some of the initial crash forces, protecting the passenger compartment to some degree."
The students disagree about the use of the word 'forces' in the statement, 'That crumpling action works to absorb some of the initial crash forces, protecting the passenger compartment to some degree',
Which one of the following students best identifies the physics of how the crumpling action protects the passengers?
| A. | Anna | '... to absorb some of the initial crash speed, protecting ...' |
| B. | Bianca | '... to absorb some of the initial crash kinetic energy, protecting ...' |
| C. | Chris | '... to absorb some of the initial crash momentum, protecting ...' |
| D. | Danshirou | '... to absorb some of the initial crash forces, protecting ...' |
PHYSICS, M2 2017 HSC 29a
A spring is used to construct a device to launch a projectile. The force `(F)` required to compress the spring is measured as a function of the displacement `(x)` by which the spring is compressed.
The potential energy stored in the compressed spring can be calculated from `E_p=(1)/(2) kx^(2)`, where `k` is the gradient of the force-displacement graph shown.
A projectile of mass 0.04 kg is launched using this device with the spring compressed by 0.08 m. Calculate the launch velocity. (4 marks)